Method of forming resist pattern

ABSTRACT

A method of forming a resist pattern including forming a first resist pattern on a substrate; applying a cross-linking composition so as to cover the first resist pattern; heating the covered first resist pattern and crosslinking an isocyanate group in the cross-linking composition with the first resist pattern; and developing the covered first resist pattern, wherein the cross-linking composition includes a blocked isocyanate compound having a protected isocyanate group.

RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2015-110851, filed May 29, 2015, the content of which is incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a method of forming a resist pattern.

BACKGROUND ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure of radial rays such as light or electronbeam through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film.

A resist material in which the exposed portions become soluble in adeveloping solution is called a positive-type, and a resist material inwhich the exposed portions become insoluble in a developing solution iscalled a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have led torapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength (and increasing the energy) of the exposure light source.Conventionally, ultraviolet radiation typified by g-line and i-lineradiation has been used, but nowadays KrF excimer lasers and ArF excimerlasers are now starting to be introduced in mass production.Furthermore, research is also being conducted into lithographytechniques that use an exposure light source having a wavelength shorter(energy higher) than these excimer lasers, such as electron beam,extreme ultraviolet radiation (EUV), and X ray.

As a method of providing a finer pattern, a method of shrinking(reducing) a hole pattern by thickening the pattern has been proposed.

For example, in Patent Document 1, a method has been described in whichthe amount of shrinkage of the resin is adjusted by using a finepattern-forming resin composition containing a cross-linking agent.

Further, in Patent Document 2, a method of thickening a pattern byforming a solvent-developed negative-tone resist pattern, causing acrosslinked layer-forming material to act on the resist pattern andforming a crosslinked layer has been described.

DOCUMENTS OF RELATED ART Patent Document

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2011-59583

[Patent Document 2] Japanese Unexamined Patent Application, FirstPublication No. 2008-310314

SUMMARY OF THE INVENTION

However, as in the invention described in Patent Document 1, in the caseof using a fine pattern-forming resin composition containing acrosslinking agent, lithographic properties of the pattern afterreduction were unsatisfactory, and there was room for furtherimprovement. Further, in Patent Document 2, for thickening the pattern,a crosslinking agent component causing a crosslinking reaction mainly bythe action of acid has been used. More specifically, the use of anamino-based crosslinking agent, a vinyl ether-based crosslinking agent,an epoxy-based crosslinking agent, and the like as a crosslinking agentcomponent has been disclosed. However, when these crosslinking agentcomponents are used, since progress of the crosslinking reaction isaffected by the amount of acid present on the resist pattern, applicableresist patterns are limited and handling properties are unsatisfactory.

The present invention takes the above circumstances into consideration,with an object of providing a method of forming a resist pattern capableof obtaining a more favorable fine pattern by reducing the pattern.

The present invention is a method of forming a resist patterncharacterized by including: a step A of forming a first resist patternon a substrate; a step B of applying a cross-linking composition so asto cover the first resist pattern; a step C of heating the covered firstresist pattern and crosslinking an isocyanate group in the cross-linkingcomposition with the first resist pattern; and a step D of developingthe covered first resist pattern, wherein the cross-linking compositionincludes a blocked isocyanate having a protected isocyanate group.

According to the present invention, it is possible to provide a methodof forming a resist pattern capable of obtaining a more favorable finepattern by reducing the pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic process diagram showing an example of step A ofthe method of forming a resist pattern according to the presentinvention.

FIG. 1B is a schematic process diagram showing an example of step B ofthe method of forming a resist pattern according to the presentinvention.

FIG. 1C is a schematic process diagram showing an example of step C ofthe method of forming a resist pattern according to the presentinvention.

FIG. 1D is a schematic process diagram showing an example of step D ofthe method of forming a resist pattern according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified.

The term “alkylene group” includes linear, branched or cyclic divalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group within an alkoxy group.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which part or all of the hydrogen atoms of an alkyl group or analkylene group have been substituted with fluorine atoms.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (namely, a resin, polymer orcopolymer).

A “structural unit derived from an acrylate ester” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of an acrylate ester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent (Rα)with which the hydrogen atom bonded to the carbon atom at the α-positionis substituted is an atom other than the hydrogen atom or a group, andexamples thereof include an alkyl group having from 1 to 5 carbon atoms,a halogenated alkyl group having from 1 to 5 carbon atoms, and ahydroxyalkyl group. A carbon atom on the α-position of an acrylate esterrefers to the carbon atom bonded to the carbonyl group, unless specifiedotherwise.

Hereafter, an acrylate ester having the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent issometimes referred to as “α-substituted acrylate ester”. Further,acrylate esters and α-substituted acrylate esters may be collectivelyreferred to as “(α-substituted) acrylate ester”.

A “structural unit derived from hydroxystyrene or a hydroxystyrenederivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of hydroxystyrene or a hydroxystyrenederivative.

The term “hydroxystyrene derivative” includes compounds in which thehydrogen atom at the α-position of hydroxystyrene has been substitutedwith another substituent such as an alkyl group or a halogenated alkylgroup; and derivatives thereof. Examples of the derivatives thereofinclude hydroxystyrene in which the hydrogen atom of the hydroxyl grouphas been substituted with an organic group and may have the hydrogenatom on the α-position substituted with a substituent; andhydroxystyrene which has a substituent other than a hydroxyl groupbonded to the benzene ring and may have the hydrogen atom on theα-position substituted with a substituent. Here, the α-position (carbonatom on the α-position) refers to the carbon atom having the benzenering bonded thereto, unless specified otherwise.

As the substituent which substitutes the hydrogen atom on the α-positionof hydroxystyrene, the same substituents as those described above forthe substituent on the α-position of the aforementioned α-substitutedacrylate ester can be mentioned.

A “structural unit derived from vinylbenzoic acid or a vinylbenzoic acidderivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of vinylbenzoic acid or a vinylbenzoic acidderivative.

The term “vinylbenzoic acid derivative” includes compounds in which thehydrogen atom at the α-position of vinylbenzoic acid has beensubstituted with another substituent such as an alkyl group or ahalogenated alkyl group; and derivatives thereof. Examples of thederivatives thereof include vinylbenzoic acid in which the hydrogen atomof the carboxy group has been substituted with an organic group and mayhave the hydrogen atom on the α-position substituted with a substituent;and vinylbenzoic acid which has a substituent other than a hydroxylgroup and a carboxy group bonded to the benzene ring and may have thehydrogen atom on the α-position substituted with a substituent. Here,the α-position (carbon atom on the α-position) refers to the carbon atomhaving the benzene ring bonded thereto, unless specified otherwise.

A “styrene derivative” refers to a compound in which the hydrogen atomon the α-position of styrene is substituted with another substituentsuch as an alkyl group, a halogenated alkyl group or the like.

A “structural unit derived from styrene” and a “structural unit derivedfrom a styrene derivative” refer to a structural unit that is formed bythe cleavage of the ethylenic double bond of styrene and a structuralunit that is formed by the cleavage of the ethylenic double bond of astyrene derivative, respectively.

As the alkyl group as a substituent on the α-position, a linear orbranched alkyl group is preferable, and specific examples include alkylgroups of 1 to 5 carbon atoms, such as a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group as the substituent onthe α-position include groups in which part or all of the hydrogen atomsof the aforementioned “alkyl group as the substituent on the α-position”are substituted with halogen atoms. Examples of the halogen atom includea fluorine atom, a chlorine atom, a bromine atom and an iodine atom, anda fluorine atom is particularly desirable.

Specific examples of the hydroxyalkyl group as the substituent on theα-position include groups in which part or all of the hydrogen atoms ofthe aforementioned “alkyl group as the substituent on the α-position”are substituted with a hydroxyl group. The number of hydroxyl groupswithin the hydroxyalkyl group is preferably 1 to 5, and most preferably1.

The case of describing “may have a substituent” includes both of thecase where the hydrogen atom (—H) is substituted with a monovalent groupand the case where the methylene group (—CH₂—) is substituted with adivalent group.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

<<Method of Forming a Resist Pattern>>

The present invention is a method of forming a resist patterncharacterized by including a step A of forming a first resist pattern ona substrate, a step B of applying a cross-linking composition so as tocover the first resist pattern, a step C of heating the covered firstresist pattern and crosslinking an isocyanate group in the cross-linkingcomposition with the first resist pattern, and a step D of developingthe covered first resist pattern, wherein the cross-linking compositionincludes a blocked isocyanate having a protected isocyanate group.Hereinafter, the method of forming a resist pattern according to thepresent invention will be described with reference to the drawings.

[Step A]

The step A is a step of forming a first resist pattern on a substrate.

In the present invention, the method of forming a first resist patternincludes: forming a resist film on a substrate using a resistcomposition to be described later; conducting exposure of the resistfilm; and developing the resist film to form a resist pattern. Accordingto the step A, as shown in FIG. 1A, a first resist pattern 2 is formedon a substrate 1.

The method for forming a first resist pattern can be performed, forexample, as follows.

Firstly, the resist composition to be described later is applied to asubstrate using a spinner or the like, and a bake treatment (postapplied bake (PAB)) is conducted at a temperature of 80 to 150° C. for40 to 120 seconds, preferably 60 to 90 seconds, to form a resist film.

Following selective exposure of the thus formed resist film, either byexposure through a mask having a predetermined pattern formed thereon(mask pattern) using an exposure apparatus such as an ArF exposureapparatus, an electron beam lithography apparatus or an EUV exposureapparatus, or by patterning via direct irradiation with an electron beamwithout using a mask pattern, baking treatment (post exposure baking(PEB)) is conducted under temperature conditions of 80 to 150° C. for 40to 120 seconds, and preferably 60 to 90 seconds.

Next, the resist film is subjected to a developing treatment.

The developing treatment is conducted using an alkali developingsolution in the case of an alkali developing process, and a developingsolution containing an organic solvent (organic developing solution) inthe case of a solvent developing process.

After the developing treatment, it is preferable to conduct a rinsetreatment. In the case of an alkali developing process, the rinsetreatment is preferably performed using pure water, whereas in the caseof a solvent developing process, the rinse treatment is preferablyperformed using a rinse liquid containing an organic solvent.

In the case of a solvent developing process, residual developingsolution or rinse liquid adhered to the pattern following the developingtreatment or rinse treatment may be removed using a supercritical fluid.

Drying is performed following the developing treatment or rinsetreatment. If desired, bake treatment (post bake) can be conductedfollowing the developing. In this manner, a resist pattern can beobtained.

In the present invention, the developing treatment may be an alkalideveloping process or may be a solvent developing process, however thesolvent developing process is preferable.

[Substrate]

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be exemplified. Specific examples of the material of the substrateinclude metals such as silicon wafer, copper, chromium, iron andaluminum; and glass. Suitable materials for the wiring pattern includecopper, aluminum, nickel, and gold.

Further, as the substrate, any one of the above-exemplified substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be exemplified. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.

Here, a “multilayer resist method” is a method in which at least onelayer of an organic film (a lower-layer organic film) and at least onelayer of a resist film (an upper-layer resist film) are provided on asubstrate, and a resist pattern formed within the upper-layer resistfilm is used as a mask to conduct patterning of the lower-layer organicfilm. This method is capable of forming a pattern with a high aspectratio. In other words, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method can be broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (a double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (a thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm is formed (a three-layer resist method).

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiations such as ArF excimerlaser, KrF excimer laser, F₂ excimer laser, extreme ultraviolet rays(EUV), vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, andsoft X-rays. The resist composition of the present invention isparticularly effective for use with a KrF excimer laser, ArF excimerlaser, EB or EUV.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long as it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

As an example of the alkali developing solution used in an alkalideveloping process, a 0.1 to 10% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) can be given.

As the organic solvent contained in the organic developing solution usedin a solvent developing process, any of the conventional organicsolvents can be used which are capable of dissolving the component (A)(prior to exposure). Specific examples of the organic solvent includepolar solvents such as ketone solvents, ester solvents, alcoholsolvents, amide solvents and ether solvents, and hydrocarbon solvents.

If desired, the organic developing solution may have a conventionaladditive blended. Examples of the additive include surfactants. Thesurfactant is not particularly limited, and for example, an ionic ornon-ionic fluorine and/or silicon surfactant can be used.

When a surfactant is added, the amount thereof based on the total amountof the organic developing solution is generally 0.001 to 5% by weight,preferably 0.005 to 2% by weight, and more preferably 0.01 to 0.5% byweight.

The developing treatment can be performed by a conventional developingmethod. Examples thereof include a method in which the substrate isimmersed in the developing solution for a predetermined time (a dipmethod), a method in which the developing solution is cast up on thesurface of the substrate by surface tension and maintained for apredetermined period (a puddle method), a method in which the developingsolution is sprayed onto the surface of the substrate (spray method),and a method in which the developing solution is continuously ejectedfrom a developing solution ejecting nozzle while scanning at a constantrate to apply the developing solution to the substrate while rotatingthe substrate at a constant rate (dynamic dispense method).

The rinse treatment using a rinse liquid (washing treatment) can beconducted by a conventional rinse method. Examples of the rinse treatingmethod include a method in which the rinse liquid is continuouslyapplied to the substrate while rotating it at a constant rate(rotational coating method), a method in which the substrate is immersedin the rinse liquid for a predetermined time (dip method), and a methodin which the rinse liquid is sprayed onto the surface of the substrate(spray method).

<Resist Composition>

In the present invention, the resist composition is preferably a resistcomposition which generates acid upon exposure and exhibits changedsolubility in a developing solution under action of acid.

In the present invention, the resist composition preferably contains abase component (A) (hereafter, referred to as “component (A)”) whichexhibits changed solubility in a developing solution under action ofacid.

When a resist film is formed using the resist composition and the formedresist film is subjected to a selective exposure, acid is generated atexposed portions, and the generated acid acts on the component (A) tochange the solubility of the component (A) in a developing solution,whereas the solubility of the component (A) in a developing solution isnot changed at unexposed portions, thereby generating difference insolubility in a developing solution between exposed portions andunexposed portions. Therefore, by subjecting the resist film todevelopment, the exposed portions are dissolved and removed to form apositive-tone resist pattern in the case of a positive resist, whereasthe unexposed portions are dissolved and removed to form a negative-toneresist pattern in the case of a negative resist.

In the present specification, a resist composition which forms apositive resist pattern by dissolving and removing the exposed portionsis called a positive resist composition, and a resist composition whichforms a negative resist pattern by dissolving and removing the unexposedportions is called a negative resist composition.

In the present invention, the resist composition may be either apositive resist composition or a negative resist composition.

Further, in the present invention, the resist composition may be appliedto an alkali developing process using an alkali developing solution inthe developing treatment at the time of resist pattern formation, or asolvent developing process using a developing solution containing anorganic solvent (organic developing solution) in the developingtreatment, and preferably a solvent developing process.

In step A, the resist composition used to form a first resist patternhas a function of generating acid upon exposure, and in the resistcomposition, the component (A) may generate acid upon exposure, or anadditive component other than the component (A) may generate acid uponexposure.

More specifically, in the present invention, the resist composition maybe

a resist composition (1) containing an acid generator component (B)which generates acid upon exposure (hereafter, referred to as “component(B)”);

a resist composition (2) in which the component (A) is a component whichgenerates acid upon exposure; or

a resist composition (3) in which the component (A) is a component whichgenerates acid upon exposure, and further containing an acid generatorcomponent (B).

That is, when the resist composition of the present embodiment is theaforementioned resist composition (2) or (3), the component (A) is a“base component which generates acid upon exposure and exhibits changedsolubility in a developing solution under action of acid”. In the casewhere the component (A) is a base component which generates acid uponexposure and exhibits changed solubility in a developing solution underaction of acid, the component (A1) described later is preferably apolymeric compound which generates acid upon exposure and exhibitschanged solubility in a developing solution under action of acid. As thepolymeric compound, a resin having a structural unit which generatesacid upon exposure can be used. As the structural unit which generatesacid upon exposure, a conventional structural unit can be used.

In the present embodiment, it is particularly desirable that the resistcomposition is the aforementioned resist composition (1).

<Component (A)>

In the present embodiment, the term “base component” refers to anorganic compound capable of forming a film, and is preferably an organiccompound having a molecular weight of 500 or more. When the organiccompound has a molecular weight of 500 or more, the film-forming abilityis improved, and a photosensitive resin pattern of nano level can beeasily formed.

The organic compound used as the base component is broadly classifiedinto non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a “lowmolecular weight compound” refers to a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. Hereafter, a “resin” refers to a polymer havinga molecular weight of 1,000 or more.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

As the component (A), a resin, a low molecular weight compound, or acombination thereof may be used.

The component (A) is a base component which exhibits increasedsolubility in a developing solution under action of acid.

In the present embodiment, the component (A) may be a component thatgenerates acid upon exposure.

In the present embodiment, the component (A) preferably contains apolymer compound (A1) having a structural unit containing an aciddecomposable group that exhibits increased polarity by the action ofacid (hereafter, sometimes referred to as “structural unit (a1)”), astructural unit containing an —SO2- containing cyclic group, alactone-containing cyclic group, a carbonate-containing cyclic group orother heterocyclic groups (hereafter, sometimes referred to as“structural unit (a2)”), and a structural unit containing a polargroup-containing aliphatic hydrocarbon group (hereafter, sometimesreferred to as “structural unit (a3)”).

(Structural Unit (a1))

The structural unit (a1) is a structural unit containing an aciddecomposable group that exhibits increased polarity by the action ofacid.

The term “acid decomposable group” refers to a group in which at least apart of the bond within the structure thereof is cleaved by the actionof an acid.

Examples of acid decomposable groups which exhibit increased polarity bythe action of an acid include groups which are decomposed by the actionof an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxyl group,an amino group and a sulfo group (—SO₃H). Among these, a sulfo group ora polar group containing —OH in the structure thereof (hereafter,sometimes referred to as “OH— containing polar group”) is preferable, asulfo group, a carboxy group or a hydroxyl group is more preferable, anda carboxy group or a hydroxyl group is particularly desirable.

More specifically, as an example of an acid decomposable group, a groupin which the aforementioned polar group has been protected with an aciddissociable group (such as a group in which the hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup) can be given.

Here, the “acid dissociable group” includes:

(i) a group in which the bond between the acid dissociable group and theadjacent atom is cleaved by the action of acid; and

(ii) a group in which one of the bonds is cleaved by the action of acid,and then a decarboxylation reaction occurs, thereby cleaving the bondbetween the acid dissociable group and the adjacent atom.

It is necessary that the acid dissociable group that constitutes theacid decomposable group is a group which exhibits a lower polarity thanthe polar group generated by the dissociation of the acid dissociablegroup. Thus, when the acid dissociable group is dissociated by theaction of acid, a polar group exhibiting a higher polarity than that ofthe acid dissociable group is generated, thereby increasing thepolarity. As a result, the polarity of the entire component (A1) isincreased. By the increase in the polarity, the solubility in an alkalideveloping solution changes and, the solubility in an organic developingsolution is relatively decreased.

The acid dissociable group is not particularly limited, and any of thegroups that have been conventionally proposed as acid dissociable groupsfor the base resins of chemically amplified resists can be used.

Examples of the acid dissociable group for protecting the carboxy groupor hydroxy group as a polar group include the acid dissociable grouprepresented by general formula (a1-r-1) shown below (hereafter, for thesake of convenience, sometimes referred to as “acetal-type aciddissociable group”).

In the formula, Ra′¹ and Ra′² represent a hydrogen atom or an alkylgroup; and Ra′³ represents a hydrocarbon group, provided that Ra′³ maybe bonded to Ra′¹ or Ra′² to form a ring.

In formula (a1-r-1), as the alkyl group for Ra′¹ and Ra′², the samealkyl groups as those described above for the alkyl groups as thesubstituent which may be bonded to the carbon atom on the α-position ofthe aforementioned α-substituted acrylic acid esters can be used,although a methyl group or ethyl group is preferable, and a methyl groupis particularly desirable.

The hydrocarbon group for Ra′³ is preferably an alkyl group of 1 to 20carbon atoms, more preferably an alkyl group of 1 to 10 carbon atoms,and still more preferably a linear or branched alkyl group. Specificexamples thereof include a methyl group, an ethyl group, a propyl group,an isopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, a neopentyl group, a1,1-dimethylethyl group, a 1,1-diethylpropyl group, a 2,2-dimethylpropylgroup and a 2,2-dimethylbutyl group.

In the case where Ra′³ represents a cyclic hydrocarbon group, the cyclichydrocarbon group may be aliphatic or aromatic, and may be polycyclic ormonocyclic. As the monocyclic alicyclic hydrocarbon group, a group inwhich 1 hydrogen atom has been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 8 carbon atoms, andspecific examples thereof include cyclopentane, cyclohexane andcyclooctane. As the polycyclic group, a group in which 1 hydrogen atomhas been removed from a polycycloalkane is preferable, and thepolycycloalkane preferably has 7 to 12 carbon atoms. Examples of thepolycycloalkane include adamantane, norbornane, isobomane,tricyclodecane and tetracyclododecane.

In the case where the hydrocarbon group is an aromatic hydrocarbongroup, examples of the aromatic ring contained in the aromatichydrocarbon group include aromatic hydrocarbon rings, such as benzene,biphenyl, fluorene, naphthalene, anthracene and phenanthrene; andaromatic hetero rings in which part of the carbon atoms constituting theaforementioned aromatic hydrocarbon rings has been substituted with ahetero atom. Examples of the hetero atom within the aromatic heterorings include an oxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich 1 hydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group); and a group in which 1 hydrogen atom ofthe aforementioned aryl group has been substituted with an alkylenegroup (an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

In the case where Ra′³ is bonded to Ra′¹ or Ra′² to form a ring, thecyclic group is preferably a 4 to 7-membered ring, and more preferably a4 to 6-membered ring. Specific examples of the cyclic group includetetrahydropyranyl group and tetrahydrofuranyl group.

Examples of the acid dissociable group for protecting the carboxy groupas a polar group include the acid dissociable group represented bygeneral formula (a1-r-2) shown below (hereafter, with respect to theacid dissociable group represented by the following formula (a1-r-2),the acid dissociable group constituted of alkyl groups is referred to as“tertiary alkyl ester-type acid dissociable group”).

In the formula, Ra′⁴ to Ra′⁶ each independently represents a hydrocarbongroup, provided that Ra′⁵ and Ra′⁶ may be mutually bonded to form aring.

As the hydrocarbon group for Ra′⁴ to Ra′⁶, the same groups as thosedescribed above for Ra′³ can be mentioned. Ra′⁴ is preferably an alkylgroup having from 1 to 5 carbon atoms. In the case where Ra′⁵ and Ra′⁶are mutually bonded to form a ring, a group represented by generalformula (a1-r2-1) shown below can be mentioned.

On the other hand, in the case where Ra′⁴ to Ra′⁶ are not mutuallybonded and independently represent a hydrocarbon group, the grouprepresented by general formula (a1-r2-2) shown below can be mentioned.

In the formulae, Ra′¹⁰ represents an alkyl group of 1 to 10 carbonatoms; Ra′¹¹ is a group which forms an aliphatic cyclic group togetherwith a carbon atom having Ra′¹⁰ bonded thereto; and Ra′¹² to Ra′¹⁴ eachindependently represents a hydrocarbon group.

In the formula (a1-r2-1), as the alkyl group of 1 to 10 carbon atoms forRa′¹⁰, the same groups as those described above for the linear orbranched alkyl group for Ra′³ in the formula (a1-r-1) are preferable. Inthe formula (a1-r2-1), as the aliphatic cyclic group which is formed byRa′¹¹, the same groups as those described above for the cyclic alkylgroup for Ra′³ in the formula (a1-r-1) are preferable.

In the formula (a1-r2-2), it is preferable that Ra′¹² and Ra′¹⁴ eachindependently represents an alkyl group of 1 to 10 carbon atoms, and itis more preferable that the alkyl group is the same group as thedescribed above for the linear or branched alkyl group for Ra′³ in theformula (a1-r-1), it is still more preferable that the alkyl group is alinear alkyl group of 1 to 5 carbon atoms, and it is particularlypreferable that the alkyl group is a methyl group or an ethyl group.

In the formula (a1-r2-2), it is preferable that Ra′¹³ is the same groupas those described above for the linear, branched or cyclic alkyl groupfor Ra′³ in the formula (a1-r-1).

Among these, the same cyclic alkyl group as those describe above forRa′³ is more preferable.

Specific examples of the aforementioned formula (a1-r2-1) are shownbelow. In the formulae shown below, “*” represents a valence bond.

Specific examples of the aforementioned formula (a1-r2-2) are shownbelow.

Examples of the acid dissociable group for protecting a hydroxy group asa polar group include the acid dissociable group represented by generalformula (a1-r-3) shown below (hereafter, referred to as “tertiaryalkyloxycarbonyl-type acid dissociable group”).

In the formula, Ra′⁷ to Ra′⁹ each independently represents an alkylgroup.

In the formula (a1-r-3), Ra′⁷ to Ra′⁹ is preferably an alkyl group of 1to 5 carbon atoms, and more preferably an alkyl group of 1 to 3 carbonatoms.

Further, the total number of carbon atoms within the alkyl group ispreferably 3 to 7, more preferably 3 to 5, and most preferably 3 or 4.

Examples of the structural unit (a1) include a structural unit derivedfrom an acrylate ester which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent andcontains an acid decomposable group which exhibits increased polarity bythe action of acid; a structural unit derived from hydroxystyrene or ahydroxystyrene derivative in which at least a part of the hydrogen atomof the hydroxy group is protected with a substituent containing an aciddecomposable group; and a structural unit derived from vinylbenzoic acidor a vinylbenzoic acid derivative in which at least a part of thehydrogen atom within —C(═O)—OH is protected with a substituentcontaining an acid decomposable group.

As the structural unit (a1), a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent is preferable.

As the structural unit (a1), structural units represented by generalformula (a1-1) or (a1-2) shown below are preferable.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Va¹represents a divalent hydrocarbon group which may have an ether bond, anurethane bond or an amide bond; n_(a1) represents an integer of 0 to 2;

Ra¹ represents an acid dissociable group represented by theaforementioned formula (a1-r-1) or (a1-r-2);

Wa¹ represents a hydrocarbon group having a valency of n_(a2)+1; n_(a2)represents an integer of 1 to 3; and Ra² represents an acid dissociablegroup represented by the aforementioned formula (a1-r-1) or (a1-r-3).

In general formula (a1-1), as the alkyl group of 1 to 5 carbon atoms forR, a linear or branched alkyl group of 1 to 5 carbon atoms ispreferable, and specific examples thereof include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl groupand a neopentyl group. The halogenated alkyl group of 1 to 5 carbonatoms represented by R is a group in which part or all of the hydrogenatoms of the aforementioned alkyl group of 1 to 5 carbon atoms have beensubstituted with halogen atoms. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

The hydrocarbon group for Va¹ may be either an aliphatic hydrocarbongroup or an aromatic hydrocarbon group. An “aliphatic hydrocarbon group”refers to a hydrocarbon group that has no aromaticity. The aliphatichydrocarbon group as the divalent hydrocarbon group for Va¹ may beeither saturated or unsaturated. In general, the aliphatic hydrocarbongroup is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

Further, as the group for Va¹, a group in which the aforementioneddivalent hydrocarbon group has been bonded via an ether bond, urethanebond or amide bond can be mentioned.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4,and most preferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

As examples of the aliphatic hydrocarbon group containing a ring in thestructure thereof, an alicyclic hydrocarbon group (a group in which twohydrogen atoms have been removed from an aliphatic hydrocarbon ring), agroup in which an alicyclic hydrocarbon group is bonded to the terminalof a linear or branched aliphatic hydrocarbon group, and a group inwhich an alicyclic hydrocarbon group is interposed within the chain of alinear or branched aliphatic hydrocarbon group, can be given. As thelinear or branched aliphatic hydrocarbon group, the same groups as thosedescribed above can be used.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic alicyclic hydrocarbon group, a groupin which 2 hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic alicyclic hydrocarbon group, a group in which two hydrogenatoms have been removed from a polycycloalkane is preferred, wherein thepolycycloalkane preferably contains 7 to 12 carbon atoms, and specificexamples of the polycycloalkane include adamantane, norbornane,isobomane, tricyclodecane and tetracyclododecane.

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring.

The aromatic hydrocarbon group as the divalent hydrocarbon group for Va¹preferably has 3 to 30 carbon atoms, more preferably 5 to 30, still morepreferably 5 to 20, still more preferably 6 to 15, and most preferably 6to 10. Here, the number of carbon atoms within a substituent(s) is notincluded in the number of carbon atoms of the aromatic hydrocarbongroup.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup include aromatic hydrocarbon rings, such as benzene, biphenyl,fluorene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include groups inwhich two hydrogen atoms have been removed from an aforementionedaromatic hydrocarbon ring (namely, arylene groups), and groups in whichone hydrogen atom from a group having one hydrogen atom removed from anaforementioned aromatic hydrocarbon ring (namely, an aryl group) issubstituted with an alkylene group (for example, groups in which onehydrogen atom is removed from the aryl group of an arylalkyl group suchas a benzyl group, phenethyl group, 1-naphthylmethyl group,2-naphthylmethyl group, 1-naphthylethyl group or 2-naphthylethyl group).The alkylene group (alkyl chain within the arylalkyl group) preferablyhas 1 to 4 carbon atom, more preferably 1 or 2, and most preferably 1.

In the aforementioned formula (a1-2), the hydrocarbon group for Wa¹having a valency of n_(a2)+1 may be either an aliphatic hydrocarbongroup or an aromatic hydrocarbon group. The aliphatic hydrocarbon grouprefers to a hydrocarbon group that has no aromaticity, and may be eithersaturated or unsaturated, but is preferably saturated. Examples of thealiphatic hydrocarbon group include a linear or branched aliphatichydrocarbon group, an aliphatic hydrocarbon group containing a ring inthe structure thereof, and a combination of the linear or branchedaliphatic hydrocarbon group and the aliphatic hydrocarbon groupcontaining a ring in the structure thereof. As the specific examplesthereof, the same groups as those described above for Va¹ in theaforementioned formula (a1-1) can be mentioned.

The valency of n_(a2)+1 is preferably divalent, trivalent ortetravalent, and divalent or trivalent is more preferable.

As the structural unit (a1--2), a structural unit represented by generalformula (a1-2-01) shown below is particularly desirable.

In the formula (a1-2-01), Ra² represents an acid dissociable grouprepresented by the aforementioned formula (a1-r-1) or (a1-r-3); n_(a2)is an integer of 1 to 3, preferably 1 or 2, and more preferably 1; c isan integer of 0 to 3, preferably 0 or 1, and more preferably 1; and R isthe same as defined above.

Specific examples of the structural units (a1-1) and (a1-2) are shownbelow. In the formulae shown below, R^(α) represents a hydrogen atom, amethyl group or a trifluoromethyl group.

In the component (A), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A) is preferably 20 to 80 mol %, more preferably 20 to 75 mol %, andstill more preferably 25 to 70 mol %. By ensuring the lower limit,various lithography properties such as sensitivity, resolution and LWRare improved. On the other hand, when the amount of the structural unit(a1) is no more than the upper limit of the above-mentioned range, agood balance can be achieved with the other structural units.

(Structural Unit (a2))

In the present embodiment, the resin component preferably includes astructural unit (a2) containing a —SO₂— containing cyclic group, alactone-containing cyclic group, a carbonate-containing cyclic group orother heterocyclic groups.

When the component (A) is used for forming a resist film, the —SO₂—containing cyclic group, the lactone-containing cyclic group, thecarbonate-containing cyclic group or other heterocyclic groups withinthe structural unit (a2) is effective in improving the adhesion betweenthe resist film and the substrate.

The later-described structural unit (a1) which contains a —SO₂—containing cyclic group, a lactone-containing cyclic group, acarbonate-containing cyclic group or other heterocyclic groups may fallunder the definition of the structural unit (a2); however, such astructural unit is regarded as a structural unit (a1), and does not fallunder the definition of the structural unit (a2).

The structural unit (a2) is preferably a structural unit represented bygeneral formula (a2-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ya²¹represents a single bond or a divalent linking group; La²¹ represents—O—, —COO—, —CON(R′)—, —OCO—, —CONHCO— or —CONHCS—; and R′ represents ahydrogen atom or a methyl group, provided that, when La²¹ represents—O—, Ya²¹ does not represent —CO—; and Ra²¹ represents a —SO₂—containing cyclic group, a lactone-containing cyclic group, acarbonate-containing cyclic group or other heterocyclic groups.

The divalent linking group for Ya²¹ is not particularly limited, andpreferable examples thereof include a divalent hydrocarbon group whichmay have a substituent and a divalent linking group containing a heteroatom.

(Divalent Hydrocarbon Group which May have a Substituent)

The hydrocarbon group as a divalent linking group may be either analiphatic hydrocarbon group or an aromatic hydrocarbon group.

An “aliphatic hydrocarbon group” refers to a hydrocarbon group that hasno aromaticity. The aliphatic hydrocarbon group may be saturated orunsaturated. In general, the aliphatic hydrocarbon group is preferablysaturated.

Examples of the aliphatic hydrocarbon group include a linear or branchedaliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof. Specifically, groupsexemplified below for Va¹ in the formula (a1-1) described later can bementioned.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms, and a carbonyl group.

As examples of the aliphatic hydrocarbon group containing a ring in thestructure thereof, a cyclic aliphatic hydrocarbon group containing ahetero atom in the ring structure thereof and may have a substituent (agroup in which two hydrogen atoms have been removed from an aliphatichydrocarbon ring), a group in which the cyclic aliphatic hydrocarbongroup is bonded to the terminal of the linear or branched aliphatichydrocarbon group, and a group in which the cyclic aliphatic group isinterposed within the aforementioned linear or branched aliphatichydrocarbon group, can be given. As the linear or branched aliphatichydrocarbon group, the same groups as those described above can be used.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

Specific examples of the cyclic aliphatic hydrocarbon group include thesame group exemplified above for Va¹ in the aforementioned formula(a1-1).

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

The cyclic aliphatic hydrocarbon group may have part of the carbon atomsconstituting the ring structure thereof substituted with a substituentcontaining a hetero atom. As the substituent containing a hetero atom,—O—, —C(═O)—O—, —S—, —S(═O)₂— or —S(═O)₂—O— is preferable.

Specific examples of the aromatic hydrocarbon group as a divalenthydrocarbon group include the same group as exemplified above for Va¹ inthe aforementioned formula (a1-1).

With respect to the aromatic hydrocarbon group, the hydrogen atom withinthe aromatic hydrocarbon group may be substituted with a substituent.For example, the hydrogen atom bonded to the aromatic ring within thearomatic hydrocarbon group may be substituted with a substituent.Examples of substituents include an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group and a hydroxyl group.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

As the alkoxy group, the halogen atom and the halogenated alkyl groupfor the substituent, the same groups as the aforementioned substituentgroups for substituting a hydrogen atom within the cyclic aliphatichydrocarbon group can be used.

(Divalent Linking Group Containing a Hetero Atom)

With respect to a divalent linking group containing a hetero atom, ahetero atom is an atom other than carbon and hydrogen, and examplesthereof include an oxygen atom, a nitrogen atom, a sulfur atom and ahalogen atom.

In the case where Ya²¹ represents a divalent linking group containing ahetero atom, preferable examples of the linking group include —O—,—C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—, —NH—C(═NH)— (whereinH may be substituted with a substituent such as an alkyl group or anacyl group), —S—, —S(═O)₂—, —S(═O)₂—O—, a group represented by generalformula —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)— O—Y²¹,—[Y²¹—C(═O)—O]_(m′)—Y²²— or —Y²¹—O—C(═O)—Y²²— [in the formulae, Y²¹ andY²² each independently represents a divalent hydrocarbon group which mayhave a substituent, and O represents an oxygen atom; and m′ representsan integer of 0 to 3.

When the divalent linking group containing a hetero atom represents—C(═O)—NH—, —NH—, or —NH—C(═NH)—, H may be substituted with asubstituent such as an alkyl group, an acyl group or the like. Thesubstituent (an alkyl group, an acyl group or the like) preferably has 1to 10 carbon atoms, more preferably 1 to 8, and most preferably 1 to 5.

In formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹,—[Y²¹—C(═O)—O]_(m′)—Y²²— and —Y²¹—O—C(═O)—Y²²—, Y²¹ and Y²² eachindependently represents a divalent hydrocarbon group which may have asubstituent. Examples of the divalent hydrocarbon group include the samegroups as those described above as the “divalent hydrocarbon group whichmay have a substituent” in the explanation of the aforementioneddivalent linking group.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m′)—Y²²—, m′represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m′)—Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

In the present embodiment, Ya²¹ preferably represents an ester bond[—C(═O)—O—], an ether bond (—O—), a linear or branched alkylene group, acombination of these, or a single bond.

In the formula (a2-1), Ra²¹ represents an —SO₂— containing cyclic group,a lactone-containing cyclic group, a heterocyclic group or acarbonate-containing cyclic group.

An “—SO₂— containing cyclic group” refers to a cyclic group having aring containing —SO₂— within the ring structure thereof, i.e., a cyclicgroup in which the sulfur atom (S) within —SO₂— forms part of the ringskeleton of the cyclic group. The ring containing —SO₂— within the ringskeleton thereof is counted as the first ring. A cyclic group in whichthe only ring structure is the ring that contains —SO₂— in the ringskeleton thereof is referred to as a monocyclic group, and a groupcontaining other ring structures is described as a polycyclic groupregardless of the structure of the other rings. The —SO₂— containingcyclic group may be either a monocyclic group or a polycyclic group.

As the —SO₂— containing cyclic group, a cyclic group containing —O—SO₂—within the ring skeleton thereof, i.e., a cyclic group containing asultone ring in which —O—S— within the —O—SO₂— group forms part of thering skeleton thereof is particularly desirable. More specific examplesof the —SO₂— containing cyclic group include groups represented bygeneral formulas (a5-r-1) to (a5-r-4) shown below.

In the formulae, each Ra′⁵¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyanogroup; R″ represents a hydrogen atom or an alkyl group; A″ represents anoxygen atom, a sulfur atom or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom; and n′ represents aninteger of 0 to 2.

In general formulae (a5-r-1) to (a5-r-4), A″ is the same as defined forA″ in general formulae (a2-r-1) to (a2-r-7) described below. The alkylgroup, alkoxy group, halogen atom, halogenated alkyl group, —COOR″,—OC(═O)R″ and hydroxyalkyl group for Ra′⁵¹ are the same as defined forRa′²¹ in general formulae (a2-r-1) to (a2-r-7) described below.

Specific examples of the groups represented by the aforementionedgeneral formulae (a5-r-1) to (a5-r-4) are shown below. In the formulaeshown below, “Ac” represents an acetyl group.

In the present embodiment, in the case where the structural unit (a2)contains a —SO₂— containing cyclic group, the structural unit (a2) isnot particularly limited as long as the log P value of the acrylic estermonomer containing the —SO₂— containing cyclic group is less than 1.2.Among them, a group represented by the aforementioned general formula(a5-r-1) is preferable, a group represented by any one of theaforementioned chemical formulae (r-s1-1-1), (r-s1-1-18), (r-s1-3-1) and(r-s1-4-1) is more preferable, and a group represented by aforementionedchemical formula (r-s1-1-1) is most preferable.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings. The lactone-containing cyclic groupmay be either a monocyclic group or a polycyclic group.

The lactone-containing cyclic group as the cyclic hydrocarbon group forR¹ is not particularly limited, and an arbitrary group may be used.Specific examples include groups represented by general formulae(a2-r-1) to (a2-r-7) shown below. Hereinbelow, “*” represents a valencebond.

In the formulae, each Ra′²¹ independently represents a hydrogen atom, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyanogroup; R″ represents a hydrogen atom or an alkyl group; A″ represents anoxygen atom, a sulfur atom or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom; n′ represents aninteger of 0 to 2; and m′ represents 0 or 1.

In general formulae (a2-r-1) to (a2-r-7) above, A″ represents an oxygenatom (—O—), a sulfur atom (—S—) or an alkylene group of 1 to 5 carbonatoms which may contain an oxygen atom or a sulfur atom. As the alkylenegroup of 1 to 5 carbon atoms for A″, a linear or branched alkylene groupis preferable, and examples thereof include a methylene group, anethylene group, an n-propylene group and an isopropylene group. Examplesof alkylene groups that contain an oxygen atom or a sulfur atom includethe aforementioned alkylene groups in which —O— or —S— is bonded to theterminal of the alkylene group or present between the carbon atoms ofthe alkylene group. Specific examples of such alkylene groups include—O—CH₂—, —CH₂—O—CH₂—, —S—CH₂— and —CH₂—S—CH₂—. As A″, an alkylene groupof 1 to 5 carbon atoms or —O— is preferable, more preferably an alkylenegroup of 1 to 5 carbon atoms, and most preferably a methylene group.Each Ra′²¹ independently represents an alkyl group, an alkoxy group, ahalogen atom, a halogenated alkyl group, —COOR″, —OC(═O)R″, ahydroxyalkyl group or a cyano group.

The alkyl group for Ra′²¹ is preferably an alkyl group of 1 to 5 carbonatoms.

The alkoxy group for Ra′²¹ is preferably an alkoxy group of 1 to 6carbon atoms.

Further, the alkoxy group is preferably a linear or branched alkoxygroup. Specific examples of the alkoxy groups include the aforementionedalkyl groups for Ra′²¹ having an oxygen atom (—O—) bonded thereto.

As examples of the halogen atom for Ra′²¹, a fluorine atom, chlorineatom, bromine atom and iodine atom can be given. Among these, a fluorineatom is preferable.

Examples of the halogenated alkyl group for Ra′²¹ include groups inwhich part or all of the hydrogen atoms within the aforementioned alkylgroup for Ra′²¹ has been substituted with the aforementioned halogenatoms. As the halogenated alkyl group, a fluorinated alkyl group ispreferable, and a perfluoroalkyl group is particularly desirable.

Specific examples of the groups represented by the aforementionedgeneral formulae (a2-r-1) to (a2-r-7) are shown below.

In the present embodiment, as the structural unit (a2), a grouprepresented by the aforementioned general formula (a2-r-1) or (a2-r-2)is preferable, and a group represented by the aforementioned chemicalformula (r-lc-1-1) or (r-lc-2-7) is more preferable.

The term “carbonate-containing cyclic group” refers to a cyclic groupincluding a ring containing a —O—C(═O)—O— structure (carbonate ring).The term “carbonate ring” refers to a single ring containing a—O—C(═O)—O— structure, and this ring is counted as the first ring. Acarbonate-containing cyclic group in which the only ring structure isthe carbonate ring is referred to as a monocyclic group, and groupscontaining other ring structures are described as polycyclic groupsregardless of the structure of the other rings. The carbonate-containingcyclic group may be either a monocyclic group or a polycyclic group.

The carbonate-containing cyclic group as the cyclic hydrocarbon groupfor R¹ is not particularly limited, and an arbitrary group may be used.Specific examples include groups represented by general formulas(ax3-r-1) to (ax3-r-3) shown below.

In the formulae, each Ra′^(x31) independently represents a hydrogenatom, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxy group, —COOR″, —OC(═O)R″, a hydroxyalkyl group ora cyano group; R″ represents a hydrogen atom or an alkyl group; A″represents an oxygen atom, a sulfur atom or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom; and q′represents 0 or 1.

In general formulae (ax3-r-1) to (ax3-r-3), A″ is the same as definedfor A″ in general formula (a2-r-1).

Examples of the alkyl group, alkoxy group, halogen atom, halogenatedalkyl group, —COOR″, —OC(═O)R″ and hydroxyalkyl group for Ra′³¹ includethe same groups as those described above in the explanation of Ra′²¹ inthe general formulas (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by the aforementionedgeneral formulae (ax3-r-1) to (ax3-r-3) are shown below.

“Heterocyclic group” is a cyclic group containing one or more atomsother than the carbon atom in addition to the carbon atoms. Examplesthereof include heterocyclic groups described later in (r-hr-1) to(r-hr-16), nitrogen-containing hetero rings, and the like. Examples ofthe nitrogen-containing hetero rings include a cycloalkyl group of 3 to8 carbon atoms which may be substituted with one or two oxo groups.Preferable examples of the cycloalkyl group include 2,5-dioxopyrrolidineand 2,6-dioxopiperidine.

As the structural unit (a2) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

When the component (A1) contains the structural unit (a2), the amount ofthe structural unit (a2) based on the combined total of all structuralunits constituting the component (A1) is preferably 1 to 80 mol %, morepreferably 5 to 70 mol %, still more preferably 10 to 65 mol %, and mostpreferably 10 to 60 mol %. When the amount of the structural unit (a2)is at least as large as the lower limit of the above-mentioned range,the effect of using the structural unit (a2) can be satisfactorilyachieved. On the other hand, when the amount of the structural unit (a2)is no more than the upper limit of the above-mentioned range, a goodbalance can be achieved with the other structural units, and variouslithography properties and pattern shape can be improved.

(Structural Unit (a3))

The structural unit (a3) is a structural unit containing a polargroup-containing aliphatic hydrocarbon group (provided that thestructural units that fall under the definition of structural units (a1)and (a2) are excluded).

When the component (A1) includes the structural unit (a3), it ispresumed that the hydrophilicity of the component (A1) is enhanced,thereby contributing to improvement in resolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which part of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups may be either a monocyclic group or a polycyclic group, and canbe selected appropriately from the multitude of groups that have beenproposed for the resins of resist compositions designed for use with ArFexcimer lasers. The cyclic group is preferably a polycyclic group, morepreferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobomane, tricyclodecane or tetracyclododecane.Of these polycyclic groups, groups in which two or more hydrogen atomshave been removed from adamantane, norbornane or tetracyclododecane arepreferred industrially.

As the structural unit (a3), there is no particular limitation as longas it is a structural unit containing a polar group-containing aliphatichydrocarbon group, and an arbitrary structural unit may be used.

The structural unit (a3) is preferably a structural unit derived from anacrylate ester which may have the hydrogen atom bonded to the carbonatom on the α-position substituted with a substituent and contains apolar group-containing aliphatic hydrocarbon group.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.

j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbomyl group.

In formula (a3-3), t′ is preferably 1. l is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbomyl group or3-norbomyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbomyl group.

As the structural unit (a3) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

The amount of the structural unit (a3) within the component (A1) basedon the combined total of all structural units constituting the component(A1) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, andstill more preferably 5 to 25 mol %.

When the amount of the structural unit (a3) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a3) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a3) is no more than the upperlimit of the above-mentioned range, a good balance can be achieved withthe other structural units.

The component (A1) may also include a structural unit (a4) which isother than the above-mentioned structural units (a1), (a2) and (a3).

(Structural Unit (a4))

The structural unit (a4) is a structural unit containing an acidnon-dissociable cyclic group. When the component (A1) includes thestructural unit (a4), dry etching resistance of the resist pattern to beformed is improved. Further, the hydrophobicity of the component (A1) isfurther improved. Increase in the hydrophobicity contributes toimprovement in terms of resolution, shape of the resist pattern and thelike, particularly in an organic solvent developing process.

An “acid non-dissociable, aliphatic cyclic group” in the structural unit(a4) refers to a cyclic group which is not dissociated by the action ofacid generated from the component (B) described later upon exposure, andremains in the structural unit.

As the structural unit (a4), a structural unit which contains anon-acid-dissociable aliphatic cyclic group, and is also derived from anacrylate ester is preferable. Examples of this cyclic group include thesame groups as those described above in relation to the aforementionedstructural unit (a1), and any of the multitude of conventional groupsused within the resin component of resist compositions for ArF excimerlasers or KrF excimer lasers (and particularly for ArF excimer lasers)can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecyl group, adamantylgroup, tetracyclododecyl group, isobornyl group, and norbomyl group isparticularly desirable. These polycyclic groups may be substituted witha linear or branched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a4-1) to (a4-7) shown below.

In the formulae, Ra represents a hydrogen atom, a methyl group or atrifluoromethyl group.

As the structural unit (a4) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

When the structural unit (a4) is included in the component (A1), theamount of the structural unit (a4) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

The component (A1) is preferably a copolymer having the structural units(a1), (a2) and (a3).

The component (A1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN) or dimethyl2,2′-azobis(isobutyrate).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

In the present embodiment, the weight average molecular weight (Mw) (thepolystyrene equivalent value determined by gel permeationchromatography) of the component (A1) is not particularly limited, butis preferably 1,000 to 50,000, more preferably 1,500 to 30,000, and mostpreferably 2,000 to 20,000. When the weight average molecular weight isno more than the upper limit of the above-mentioned range, the resistcomposition exhibits a satisfactory solubility in a resist solvent. Onthe other hand, when the weight average molecular weight is at least aslarge as the lower limit of the above-mentioned range, dry etchingresistance and the cross-sectional shape of the resist pattern becomesatisfactory.

As the component (A1), one type may be used alone, or two or more typesmay be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 25% by weight or more,more preferably 50% by weight or more, still more preferably 75% byweight or more, and may be even 100% by weight. When the amount of thecomponent (A1) is 25% by weight or more, various lithography propertiesare improved.

In the present embodiment, as the component (A), one type may be used,or two or more types of compounds may be used in combination.

In the present embodiment, the amount of the component (A) can beappropriately adjusted depending on the thickness of the resist film tobe formed, and the like.

<Acid Generator Component; Component (B)>

In the present embodiment, the resist composition may further include anacid generator component (B) (hereafter, referred to as “component (B)”)which generates acid upon exposure. As the component (B), there is noparticular limitation, and any of the known acid generators used inconventional chemically amplified resist compositions can be used.

Examples of these acid generators are numerous, and include onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate acid generators; diazomethane acid generators such as bisalkylor bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators. Among these, it is preferable to use anonium salt acid generator.

As the onium salt acid generator, a compound represented by generalformula (b-1) below (hereafter, sometimes referred to as “component(b-1)”), a compound represented by general formula (b-2) below(hereafter, sometimes referred to as “component (b-2)”) or a compoundrepresented by general formula (b-3) below (hereafter, sometimesreferred to as “component (b-3)”) may be used.

In the formulae, R¹⁰¹ and R¹⁰⁴ to R¹⁰⁸ each independently represents acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent, provided that R¹⁰⁴ and R¹⁰⁵ may be mutually bondedto form a ring; R¹⁰⁶ and R¹⁰⁷ may be mutually bonded to form a ring;R¹⁰² represents a fluorine atom or a fluorinated alkyl group of 1 to 5carbon atoms; Y¹⁰¹ represents a single bond or a divalent linking groupcontaining an oxygen atom; V¹⁰¹ to V¹⁰³ each independently represents asingle bond, an alkylene group or a fluorinated alkylene group; L¹⁰¹ toL¹⁰² each independently represents a single bond or an oxygen atom; L¹⁰³to L¹⁰⁵ each independently represents a single bond, —CO— or —SO₂—; andM′^(m+) represents an organic cation having a valency of m.

{Anion Moiety}

—Anion Moiety of Component (b-1)

In the formula (b-1), R¹⁰¹ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent.

(Cyclic Group which May have a Substituent in R¹⁰¹)

The cyclic group is preferably a cyclic hydrocarbon group, and thecyclic hydrocarbon group may be either an aromatic hydrocarbon group oran aliphatic hydrocarbon group.

As the aromatic hydrocarbon group for R¹⁰¹, groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring described abovein relation to the divalent aromatic hydrocarbon group for Va¹ in theformula (a1-1) or an aromatic compound containing two or more aromaticring can be mentioned, and a phenyl group or a naphthyl group ispreferable.

As the cyclic aliphatic hydrocarbon group for R¹⁰¹, groups in which onehydrogen atom has been removed from a monocycloalkane or apolycycloalkane exemplified above in the explanation of the divalentaliphatic hydrocarbon group for Va1 in the formula (a1-1) can bementioned, and an adamantyl group or a norbomyl group is preferable.

Further, the cyclic hydrocarbon group for R¹⁰¹ may contain a hetero atomlike as a heterocycle, and specific examples thereof includelactone-containing cyclic groups represented by the aforementionedgeneral formulas (a2-r-1) to (a2-r-7), —SO₂— containing cyclic groupsrepresented by the aforementioned formulas (a5-r-1) to (a5-r-4) andheterocycles shown below as (r-hr-1) to (r-hr-16).

As the substituent for the cyclic hydrocarbon group for R¹⁰¹, an alkylgroup, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxyl group, a carbonyl group, a nitro group or the like can be used.

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Example of the halogenated alkyl group as the substituent includes agroup in which a part or all of the hydrogen atoms within an alkyl groupof 1 to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propylgroup, an n-butyl group or a tert-butyl group) have been substitutedwith the aforementioned halogen atoms.

(Chain-Like Alkyl Group which May have a Substituent in R¹⁰¹)

The chain-like alkyl group for R¹⁰¹ may be linear or branched.

The linear alkyl group preferably has 1 to 20 carbon atoms, morepreferably 1 to 15, and most preferably 1 to 10. Specific examplesinclude a methyl group, an ethyl group, a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a nonylgroup, a decyl group, an undecyl group, a dodecyl group, a tridecylgroup, an isotridecyl group, a tetradecyl group, a pentadecyl group, ahexadecyl group, an isohexadecyl group, a heptadecyl group, an octadecylgroup, a nonadecyl group, an icosyl group, a henicosyl group and adocosyl group.

The branched alkyl group preferably has 3 to 20 carbon atoms, morepreferably 3 to 15, and most preferably 3 to 10. Specific examplesinclude a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropylgroup, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutylgroup, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentylgroup, a 2-methylpentyl group, a 3-methylpentyl group and a4-methylpentyl group.

(Chain-Like Alkenyl Group which May have a Substituent in R¹⁰¹)

The chain-like alkenyl group for R¹⁰¹ may be linear or branched, andpreferably has 2 to 10 carbon atoms, more preferably 2 to 5 carbonatoms, still more preferably 2 to 4 carbon atoms, and most preferably 3carbon atoms. Examples of linear alkenyl groups include a vinyl group, apropenyl group (an allyl group) and a butynyl group. Examples ofbranched alkenyl groups include a 1-methylpropenyl group and a2-methylpropenyl group.

Among the above-mentioned examples, as the chain-like alkenyl group, apropenyl group is particularly desirable.

As the substituent for the chain-like alkyl group or alkenyl group forR¹⁰¹, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxyl group, a carbonyl group, a nitro group, an amino group, acyclic group for R¹⁰¹ or the like can be used.

Among these examples, as R¹⁰¹, a cyclic group which may have asubstituent is preferable, and a cyclic hydrocarbon group which may havea substituent is more preferable. Specifically, a phenyl group, anaphthyl group, a group in which one or more hydrogen atoms have beenremoved from a polycycloalkane, a lactone-containing cyclic grouprepresented by any one of the aforementioned formula (a2-r-1) to(a2-r-7), and an —SO₂— containing cyclic group represented by any one ofthe aforementioned formula (a5-r-1) to (a5-r-4).

In formula (b-1), Y¹⁰¹ represents a single bond or a divalent linkinggroup containing an oxygen atom.

In the case where Y¹⁰¹ is a divalent linking group containing an oxygenatom, Y¹⁰¹ may contain an atom other than an oxygen atom. Examples ofatoms other than an oxygen atom include a carbon atom, a hydrogen atom,a sulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonylgroup (—O—C(═O)—), an amido bond (—C(═O)—NH—), a carbonyl group(—C(═O)—) and a carbonate bond (—O—C(═O)—O—); and combinations of theaforementioned non-hydrocarbon, oxygen atom-containing linking groupswith an alkylene group. Furthermore, the combinations may have asulfonyl group (—SO₂—) bonded thereto. As the combination, the linkinggroup represented by formulas (y-a1-1) to (y-a1-7) shown below can bementioned.

In the formulae, V′¹⁰¹ represents a single bond or an alkylene group of1 to 5 carbon atoms; V′¹⁰² represents a divalent saturated hydrocarbongroup of 1 to 30 carbon atoms.

The divalent saturated hydrocarbon group for V′¹⁰² is preferably analkylene group of 1 to 30 carbon atoms.

The alkylene group for V′¹⁰¹ and V′¹⁰² may be a linear alkylene group ora branched alkylene group, and a linear alkylene group is preferable.

Specific examples of the alkylene group for V′¹⁰¹ and V′¹⁰² include amethylene group [—CH₂—]; an alkylmethylene group, such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and—C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group, suchas —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; atrimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; analkyltrimethylene group, such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group,such as —CH(CH₃)CH₂CH₂CH₂—, —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylenegroup [—CH₂CH₂CH₂CH₂CH₂—].

Further, part of methylene group within the alkylene group for V′¹⁰¹ andV′¹⁰² may be substituted with a divalent aliphatic cyclic group of 5 to10 carbon atoms. The aliphatic cyclic group is preferably a divalentgroup in which one hydrogen atom has been removed from the cyclicaliphatic hydrocarbon group for Ra′³ in the aforementioned formula(a1-r-1), and a cyclohexylene group, 1,5-adamantylene group or2,6-adamantylene group is more preferable.

Y¹⁰¹ is preferably a divalent linking group containing an ether bond oran ester bond, and groups represented by the aforementioned formulas(y-a1-1) to (y-a1-5) are preferable.

In formula (b-1), V¹⁰¹ represents a single bond, an alkylene group or afluorinated alkylene group. The alkylene group and the fluorinatedalkylene group for V¹⁰¹ preferably has 1 to 4 carbon atoms. Examples ofthe fluorinated alkylene group for V¹⁰¹ include a group in which part orall of the hydrogen atoms within the alkylene group for V¹⁰¹ have beensubstituted with fluorine atoms. Among these examples, as V¹⁰¹, a singlebond or a fluorinated alkylene group of 1 to 4 carbon atoms ispreferable.

In formula (b-1), R¹⁰² represents a fluorine atom or a fluorinated alkylgroup of 1 to 5 carbon atoms. R¹⁰² is preferably a fluorine atom or aperfluoroalkyl group of 1 to 5 carbon atoms, and more preferably afluorine atom.

As specific examples of anion moieties of the formula (b-1),

in the case where Y¹⁰¹ represents a single bond, a fluorinatedalkylsulfonate anion such as a trifluoromethanesulfonate anion or aperfluorobutanesulfonate anion can be mentioned; and in the case whereY¹⁰¹ represents a divalent linking group containing an oxygen atom,anions represented by formulae (an-1) to (an-3) shown below can bementioned.

In the formulae, R″¹⁰¹ represents an aliphatic cyclic group which mayhave a substituent, a group represented by any one of the aforementionedformulae (r-hr-1) to (r-hr-6) or a chain-like alkyl group which may havea substituent; R″¹⁰² represents an aliphatic cyclic group which may havea substituent, a lactone-containing cyclic group represented by any oneof the aforementioned formulae (a2-r-1) to (a2-r-7) or an —SO₂—containing cyclic group represented by any one of the aforementionedgeneral formulae (a5-r-1) to (a5-r-4); R″¹⁰³ represents an aromaticcyclic group which may have a substituent, an aliphatic cyclic groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent; V″¹⁰¹ represents a fluorinated alkylene group; L″¹⁰¹represents —C(═O)— or —SO₂—; v″ represents an integer of 0 to 3; q″represents an integer of 1 to 20; and n″ represents 0 or 1.

As the aliphatic cyclic group for R″¹⁰¹, R″¹⁰² and R″¹⁰³ which may havea substituent, the same groups as the cyclic aliphatic hydrocarbon groupfor R¹⁰¹ described above are preferable. As the substituent, the samegroups as those described above for substituting the cyclic aliphatichydrocarbon group for R¹⁰¹ can be mentioned.

As the aromatic cyclic group for R″¹⁰³ which may have a substituent, thesame groups as the aromatic hydrocarbon group for the cyclic hydrocarbongroup represented by R¹⁰¹ described above are preferable. Thesubstituent is the same as defined for the substituent for the aromatichydrocarbon group represented by R¹⁰¹.

As the chain-like alkyl group for R″¹⁰¹ which may have a substituent,the same groups as those described above for R¹⁰¹ are preferable. As thechain-like alkenyl group for R″¹⁰³ which may have a substituent, thesame groups as those described above for R¹⁰¹ are preferable. V″¹⁰¹ ispreferably a fluorinated alkylene group of 1 to 3 carbon atoms, and mostpreferably —CF₂—, —CF₂CF₂—, —CHFCF₂—, —CF(CF₃)CF₂— or —CH(CF₃)CF₂—.

—Anion Moiety of Component (b-2)

In formula (b-2), R¹⁰⁴ and R¹⁰⁵ each independently represents a cyclicgroup which may have a substituent, a chain-like alkyl group which mayhave a substituent or a chain-like alkenyl group which may have asubstituent, and is the same as defined for R¹⁰¹ in formula (b-1). R¹⁰⁴and R¹⁰⁵ may be mutually bonded to form a ring.

As R¹⁰⁴ and R¹⁰⁵, a chain-like alkyl group which may have a substituentis preferable, and a linear or branched alkyl group or a linear orbranched fluorinated alkyl group is more preferable.

The chain-like alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbonatoms. The smaller the number of carbon atoms of the chain-like alkylgroup for R¹⁰⁴ and R¹⁰⁵ within the above-mentioned range of the numberof carbon atoms, the more the solubility in a resist solvent isimproved. Therefore, smaller number is preferable. Further, in thechain-like alkyl group for R¹⁰⁴ and R¹⁰⁵, it is preferable that thenumber of hydrogen atoms substituted with fluorine atoms is as large aspossible because the acid strength increases and the transparency tohigh energy radiation of 200 nm or less or electron beam is improved.The fluorination ratio of the chain-like alkyl group is preferably from70 to 100%, more preferably from 90 to 100%, and it is particularlydesirable that the chain-like alkyl group be a perfluoroalkyl group inwhich all hydrogen atoms are substituted with fluorine atoms.

In formula (b-2), V¹⁰² and V¹⁰³ each independently represents a singlebond, an alkylene group or a fluorinated alkylene group, and is the sameas defined for V¹⁰¹ in formula (b-1).

In formula (b-2), L¹⁰¹ and L¹⁰² each independently represents a singlebond or an oxygen atom.

—Anion Moiety of Component (b-3)

In formula (b-3), R¹⁰⁶ to R¹⁰⁸ each independently represents a cyclicgroup which may have a substituent, a chain-like alkyl group which mayhave a substituent or a chain-like alkenyl group which may have asubstituent, and is the same as defined for R¹⁰¹ in formula (b-1).

L¹⁰³ to L¹⁰⁵ each independently represents a single bond, —CO— or —SO₂—.

{Cation Moiety}

In formulae (b-1), (b-2) and (b-3), M′^(m+) represents an organic cationhaving a valency of m, preferably a sulfonium cation or an iodoniumcation, and most preferably a cation represented by any one of formulae(ca-1) to (ca-4) shown below.

In the formulae, R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² each independentlyrepresents an aryl group which may have a substituent, an alkyl groupwhich may have a substituent or an alkenyl group which may have asubstituent, provided that two of R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, or R²¹¹and R²¹² may be mutually bonded to form a ring with the sulfur atom;R²⁰⁸ and R²⁰⁹ each independently represents a hydrogen atom or an alkylgroup of 1 to 5 carbon atoms; R²¹⁰ represents an aryl group which mayhave a substituent, an alkyl group which may have a substituent, analkenyl group which may have a substituent or an —SO₂— containing cyclicgroup which may have a substituent; L²⁰¹ represents —C(═O)— or—C(═O)—O—; Y²⁰¹ each independently represents an arylene group, analkylene group or an alkenylene group; x represents 1 or 2; and W²⁰¹represents a linking group having a valency of (x+1).

As the aryl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹², an unsubstituted arylgroup of 6 to 20 carbon atoms can be mentioned, and a phenyl group or anaphthyl group is preferable.

The alkyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² is preferably achain-like or cyclic alkyl group having 1 to 30 carbon atoms.

The alkenyl group for R²⁰¹ to R²⁰⁷, R²¹¹ and R²¹² preferably has 2 to 10carbon atoms.

Specific examples of the substituent which R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹²may have include an alkyl group, a halogen atom, a halogenated alkylgroup, a carbonyl group, a cyano group, an amino group, an aryl group,an arylthio group and groups represented by formulae (ca-r-1) to(ca-r-7) shown below.

The aryl group within the arylthio group as the substituent is the sameas defined for R¹⁰¹, and specific examples include a phenylthio groupand a biphenylthio group.

In the formulae, R′²⁰¹ each independently represents a hydrogen atom, acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent or a chain-like alkenyl group which mayhave a substituent.

As the cyclic group which may have a substituent, the chain-like alkylgroup which may have a substituent and the chain-like alkenyl groupwhich may have a substituent for R′²⁰¹, the same groups as thosedescribed above for R¹⁰¹ in formula (b-1) can be mentioned. As thecyclic group which may have a substituent and chain-like alkyl groupwhich may have a substituent, the same groups as those described abovefor the acid dissociable group represented by the aforementioned formula(a1-r-2) can be also mentioned.

When R²⁰¹ to R²⁰³, R²⁰⁶, R²⁰⁷, R²¹¹ and R²¹² are mutually bonded to forma ring with the sulfur atom, these groups may be mutually bonded via ahetero atom such as a sulfur atom, an oxygen atom or a nitrogen atom, ora functional group such as a carbonyl group, —SO—, —SO₂—, —SO₃—, —COO—,—CONH— or —N(RN)— (wherein RN represents an alkyl group of 1 to 5 carbonatoms). The ring containing the sulfur atom in the skeleton thereof ispreferably a 3 to 10-membered ring, and most preferably a 5 to7-membered ring, including the sulfur atom. Specific examples of thering formed include a thiophene ring, a thiazole ring, a benzothiophenering, a thianthrene ring, a benzothiophene ring, a dibenzothiophenering, a 9H-thioxanthene ring, a thioxanthone ring, a phenoxathiin ring,a tetrahydrothiophenium ring, and a tetrahydrothiopyranium ring.

R²⁰⁸ and R²⁰⁹ each independently represents a hydrogen atom or an alkylgroup of 1 to 5 carbon atoms, and preferably a hydrogen atom or an alkylgroup of 1 to 3 carbon atoms, provided that, in the case of an alkylgroup, the groups may be mutually bonded to form a ring.

R²¹⁰ represents an aryl group which may have a substituent, an alkylgroup which may have a substituent, an alkenyl group which may have asubstituent, or an —SO₂— containing cyclic group which may have asubstituent.

Examples of the aryl group for R²¹⁰ include an unsubstituted aryl groupof 6 to 20 carbon atoms, and a phenyl group or a naphthyl group ispreferable.

As the alkyl group for R²¹⁰, a chain-like or cyclic alkyl group having 1to 30 carbon atoms is preferable.

The alkenyl group for R²¹⁰ preferably has 2 to 10 carbon atoms.

As the —SO₂— containing cyclic group for R²¹⁰ which may have asubstituent, the same “—SO₂— containing cyclic groups” as thosedescribed above for Ra²¹ in the aforementioned general formula (a2-1)can be mentioned, and the group represented by the aforementionedgeneral formula (a5-r-1) is preferable.

Each Y²⁰¹ independently represents an arylene group, an alkylene groupor an alkenylene group.

Examples of the arylene group for Y²⁰¹ include groups in which onehydrogen atom has been removed from an aryl group given as an example ofthe aromatic hydrocarbon group for R¹⁰¹ in the aforementioned formula(b-1).

The alkylene group and the alkenylene group for Y²⁰¹ is the same asdefined for the aliphatic hydrocarbon group as the divalent linkinggroup represented by Va¹ in the aforementioned general formula (a1-1).

In the formula (ca-4), x represents 1 or 2.

W²⁰¹ represents a linking group having a valency of (x+1), i.e., adivalent or trivalent linking group.

As the divalent linking group for W²⁰¹, a divalent hydrocarbon groupwhich may have a substituent is preferable, and as examples thereof, thesame hydrocarbon groups as those described above for Ya²¹ in the generalformula (a2-1) can be mentioned. The divalent linking group for W²⁰¹ maybe linear, branched or cyclic, and cyclic is more preferable. Amongthese, an arylene group having two carbonyl groups, each bonded to theterminal thereof is preferable. Examples of the arylene group include aphenylene group and a naphthylene group, and a phenylene group isparticularly desirable.

As the trivalent linking group for W²⁰¹, a group in which one hydrogenatom has been removed from the aforementioned divalent linking group forW²⁰¹ and a group in which the divalent linking group has been bonded toanother divalent linking group can be mentioned. The trivalent linkinggroup for W²⁰¹ is preferably a group in which 2 carbonyl groups arebonded to an arylene group.

Specific examples of preferable cations represented by formula (ca-1)include cations represented by formulae (ca-1-1) to (ca-1-63) shownbelow.

In the formulae, g1, g2 and g3 represent recurring numbers, wherein g1is an integer of 1 to 5, g2 is an integer of 0 to 20, and g3 is aninteger of 0 to 20.

In the formulae, R″²⁰¹ represents a hydrogen atom or a substituent, andas the substituent, the same groups as those described above forsubstituting R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² can be mentioned.

Specific examples of preferable cations represented by formula (ca-3)include cations represented by formulae (ca-3-1) to (ca-3-6) shownbelow.

Specific examples of preferable cations represented by formula (ca-4)include cations represented by formulae (ca-4-1) and (ca-4-2) shownbelow.

As the component (B), one type of these acid generators may be usedalone, or two or more types may be used in combination.

When the resist composition of the present embodiment contains thecomponent (B), the amount of the component (B) relative to 100 parts byweight of the component (A) is preferably within a range from 0.5 to 60parts by weight, more preferably from 1 to 50 parts by weight, and stillmore preferably from 1 to 40 parts by weight. When the amount of thecomponent (B) is within the above-mentioned range, formation of a resistpattern can be satisfactorily performed. Further, by virtue of theabove-mentioned range, when each of the components of the resistcomposition is dissolved in an organic solvent, a uniform solution canbe obtained and the storage stability becomes satisfactory.

<Basic Compound Component; Component (D)>

Moreover, in the present embodiment, the resist composition may includean acid diffusion control agent component (hereafter, frequentlyreferred to as “component (D)”), in addition to the component (A), or inaddition to the component (A) and the component (B).

The component (D) functions as an acid diffusion control agent, i.e., aquencher which traps the acid generated from the component (B) and thelike upon exposure.

In the present embodiment, the component (D) may be a photodecomposablebase (D1) (hereafter, referred to as “component (D1)”) which isdecomposed upon exposure and then loses the ability of controlling ofacid diffusion, or a nitrogen-containing organic compound (D2)(hereafter, referred to as “component (D2)”) which does not fall underthe definition of component (D1).

[Component (D1)]

When a resist pattern is formed using a resist composition containingthe component (D1), the contrast between exposed portions and unexposedportions is improved.

The component (D1) is not particularly limited, as long as it isdecomposed upon exposure and then loses the ability of controlling ofacid diffusion. As the component (D1), at least one compound selectedfrom the group consisting of a compound represented by general formula(d1-1) shown below (hereafter, referred to as “component (d1-1)”), acompound represented by general formula (d1-2) shown below (hereafter,referred to as “component (d1-2)”) and a compound represented by generalformula (d1-3) shown below (hereafter, referred to as “component(d1-3)”) is preferably used.

At exposed portions, the components (d1-1) to (d1-3) are decomposed andthen lose the ability of controlling of acid diffusion (i.e., basicity),and therefore the components (d1-1) to (d1-3) cannot function as aquencher, whereas at unexposed portions, the components (d1-1) to (d1-3)function as a quencher.

In the formulae, Rd¹ to Rd⁴ represent a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, provided that,the carbon atom adjacent to the sulfur atom within the Rd² in theformula (d1-2) has no fluorine atom bonded thereto; Yd¹ represents asingle bond or a divalent linking group; and M^(m+) each independentlyrepresents an organic cation having a valency of m.

{Component (d1-1)}

—Anion Moiety

In formula (d1-1), Rd¹ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹

Among these, as the group for Rd¹, an aromatic hydrocarbon group whichmay have a substituent, an aliphatic cyclic group which may have asubstituent and a chain-like hydrocarbon group which may have asubstituent are preferable. As the substituents which these groups mayhave, a hydroxyl group, a fluorine atom or a fluorinated alkyl group ispreferable.

The aromatic hydrocarbon group is preferably a phenyl group or anaphthyl group.

Examples of the aliphatic cyclic group include groups in which one ormore hydrogen atoms have been removed from a polycycloalkane such asadamantane, norbomane, isobomane, tricyclodecane or tetracyclododecane.

As the chain-like hydrocarbon group, a chain-like alkyl group ispreferable. The chain-like alkyl group preferably has 1 to 10 carbonatoms, and specific examples thereof include a linear alkyl group suchas a methyl group, an ethyl group, a propyl group, a butyl group, apentyl group, a hexyl group, a heptyl group, an octyl group, a nonylgroup or a decyl group, and a branched alkyl group such as a1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a2-methylpentyl group, a 3-methylpentyl group or a 4-methylpentyl group.

In the case where the chain-like alkyl group is a fluorinated alkylgroup having a fluorine atom or a fluorinated alkyl group as asubstituent, the fluorinated alkyl group preferably has 1 to 11 carbonatoms, more preferably 1 to 8 carbon atoms, and still more preferably 1to 4 carbon atoms. The fluorinated alkyl group may contain an atom otherthan fluorine. Examples of the atom other than fluorine include anoxygen atom, a carbon atom, a hydrogen atom, a sulfur atom and anitrogen atom.

As Rd¹, a fluorinated alkyl group in which part or all of the hydrogenatoms constituting a linear alkyl group have been substituted withfluorine atom(s) is preferable, and a fluorinated alkyl group in whichall of the hydrogen atoms constituting a linear alkyl group have beensubstituted with fluorine atoms (i.e., a linear perfluoroalkyl group) ismore preferable.

Specific examples of preferable anion moieties for the component (d1-1)are shown below.

—Cation Moiety

In formula (d1-1), M^(m+) represents an organic cation having a valencyof m.

The organic cation for M^(m+) is not particularly limited, and examplesthereof include the same cation moieties as those represented by theaforementioned formulas (ca-1) to (ca-4), and cation moietiesrepresented by the aforementioned formulas (ca-1-1) to (ca-1-63) arepreferable.

As the component (d1-1), one type of compound may be used, or two ormore types of compounds may be used in combination.

{Component (d1-2)}

—Anion Moiety

In formula (d1-2), Rd² represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹.

The carbon atom adjacent to the sulfur atom within Rd² group has nofluorine atom bonded thereto (i.e., the carbon atom adjacent to thesulfur atom within Rd² group is not substituted with a fluorine atom).As a result, the anion of the component (d1-2) becomes an appropriatelyweak acid anion, thereby improving the quenching ability of thecomponent (D).

As Rd², an aliphatic cyclic group which may have a substituent ispreferable, and a group in which one or more hydrogen atoms have beenremoved from adamantane, norbomane, isobomane, tricyclodecane,tetracyclododecane or camphor (which may have a substituent) is morepreferable.

The hydrocarbon group for Rd² may have a substituent. As thesubstituent, the same groups as those described above for substitutingthe hydrocarbon group (e.g., aromatic hydrocarbon group, aliphatichydrocarbon group) for Rd¹ in the formula (d1-1) can be mentioned.

Specific examples of preferable anion moieties for the component (d1-2)are shown below.

—Cation Moiety

In formula (d1-2), M^(m+) is an organic cation having a valency of m,and is the same as defined for M^(m+) in the aforementioned formula(d1-1).

As the component (d1-2), one type of compound may be used, or two ormore types of compounds may be used in combination.

{Component (d1-3)}

—Anion Moiety

In formula (d1-3), Rd³ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹, and a cyclic group containing afluorine atom, a chain-like alkyl group or a chain-like alkenyl group ispreferable. Among these, a fluorinated alkyl group is preferable, andthe same fluorinated alkyl groups as those described above for Rd¹ aremore preferable.

In formula (d1-3), Rd⁴ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and is the samegroups as those defined above for R¹⁰¹.

Among these, an alkyl group which may have substituent, an alkoxy groupwhich may have substituent, an alkenyl group which may have substituentor a cyclic group which may have substituent is preferable.

The alkyl group for Rd⁴ is preferably a linear or branched alkyl groupof 1 to 5 carbon atoms, and specific examples include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl group,and a neopentyl group. Part of the hydrogen atoms within the alkyl groupfor Rd⁴ may be substituted with a hydroxy group, a cyano group or thelike.

The alkoxy group for Rd⁴ is preferably an alkoxy group of 1 to 5 carbonatoms, and specific examples thereof include a methoxy group, an ethoxygroup, an n-propoxy group, an iso-propoxy group, an n-butoxy group and atert-butoxy group. Among these, a methoxy group and an ethoxy group arepreferable.

As the alkenyl group for Rd⁴, the same groups as those described abovefor R¹⁰¹ can be mentioned, and a vinyl group, a propenyl group (an allylgroup), a 1-methylpropenyl group and a 2-methylpropenyl group arepreferable. These groups may have an alkyl group of 1 to 5 carbon atomsor a halogenated alkyl group of 1 to 5 carbon atoms as a substituent.

As the cyclic group for Rd⁴, the same groups as those described abovefor R¹⁰¹ can be mentioned. Among these, as the cyclic group, analicyclic group (e.g., a group in which one or more hydrogen atoms havebeen removed from a cycloalkane such as cyclopentane, cyclohexane,adamantane, norbornane, isobomane, tricyclodecane or tetracyclododecane)or an aromatic group (e.g., a phenyl group or a naphthyl group) ispreferable. When Rd⁴ is an alicyclic group, the resist composition canbe satisfactorily dissolved in an organic solvent, thereby improving thelithography properties. Alternatively, when Rd⁴ is an aromatic group,the resist composition exhibits an excellent photoabsorption efficiencyin a lithography process using EUV or the like as the exposure source,thereby resulting in the improvement of the sensitivity and thelithography properties.

In formula (d1-3), Yd¹ represents a single bond or a divalent linkinggroup.

The divalent linking group for Yd¹ is not particularly limited, andexamples thereof include a divalent hydrocarbon group (aliphatichydrocarbon group, or aromatic hydrocarbon group) which may have asubstituent and a divalent linking group containing a hetero atom. Assuch groups, the same divalent linking groups as those described abovefor Ya²¹ in the formula (a2-1) can be mentioned.

As Yd¹, a carbonyl group, an ester bond, an amide bond, an alkylenegroup or a combination of these is preferable. As the alkylene group, alinear or branched alkylene group is more preferable, and a methylenegroup or an ethylene group is still more preferable.

Specific examples of preferable anion moieties for the component (d1-3)are shown below.

—Cation Moiety

In formula (d1-3), M^(m+) is an organic cation having a valency of m,and is the same as defined for M^(m+) in the aforementioned formula(d1-1).

As the component (d1-3), one type of compound may be used, or two ormore types of compounds may be used in combination.

As the component (D1), one type of the aforementioned components (d1-1)to (d1-3), or at least two types of the aforementioned components (d1-1)to (d1-3) can be used in combination.

The amount of the component (D1) relative to 100 parts by weight of thecomponent (A) is preferably within a range from 0.5 to 10.0 parts byweight, more preferably from 0.5 to 8.0 parts by weight, and still morepreferably from 1 to 8 parts by weight.

When the amount of the component (D1) is at least as large as the lowerlimit of the above-mentioned range, excellent lithography properties andexcellent resist pattern shape can be obtained. On the other hand, whenthe amount of the component (D1) is no more than the upper limit of theabove-mentioned range, sensitivity can be maintained at a satisfactorylevel, and through-put becomes excellent.

The production methods of the components (d1-1) and (d1-2) are notparticularly limited, and the components (d1-1) and (d1-2) can beproduced by conventional methods.

The amount of the component (D1) relative to 100 parts by weight of thecomponent (A) is preferably within a range from 0.5 to 10.0 parts byweight, more preferably from 0.5 to 8.0 parts by weight, and still morepreferably from 1.0 to 8.0 parts by weight. When the amount of thecomponent (D1) is at least as large as the lower limit of theabove-mentioned range, excellent lithography properties and excellentresist pattern shape can be obtained. On the other hand, when the amountof the component (D1) is no more than the upper limit of theabove-mentioned range, sensitivity can be maintained at a satisfactorylevel, and through-put becomes excellent.

(Component (D2))

The component (D) may contain a nitrogen-containing organic compound(D2) (hereafter, referred to as component (D2)) which does not fallunder the definition of component (D1).

The component (D2) is not particularly limited, as long as it functionsas an acid diffusion control agent, and does not fall under thedefinition of the component (D1). As the component (D2), any of theconventionally known compounds may be selected for use. Among these, analiphatic amine, particularly a secondary aliphatic amine or tertiaryaliphatic amine is preferable.

An aliphatic amine is an amine having one or more aliphatic groups, andthe aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 12 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine. Among these, trialkylamines of 5 to 10 carbon atomsare preferable, and tri-n-pentylamine and tri-n-octylamine areparticularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1, 5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris {2-(2-methoxyethoxy)ethyl}amine,tris {2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine and triethanolaminetriacetate, and triethanolamine triacetate is preferable.

Further, as the component (D2), an aromatic amine may be used.

Examples of aromatic amines include aniline, pyridine,4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole andderivatives thereof, as well as diphenylamine, triphenylamine,tribenzylamine, 2,6-diisopropylaniline and N-tert-butoxycarbonylpyrrolidine.

As the component (D2), one type of compound may be used alone, or two ormore types may be used in combination.

The component (D2) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D2) is within theabove-mentioned range, the shape of the resist pattern and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer are improved.

As the component (D), one type of compound may be used, or two or moretypes of compounds may be used in combination.

In the present embodiment, when the resist composition contains thecomponent (D), the amount of the component (D) relative to 100 parts byweight of the component (A) is preferably within a range from 0.1 to 15parts by weight, more preferably from 0.3 to 12 parts by weight, andstill more preferably from 0.5 to 12 parts by weight. When the amount ofthe component (D) is at least as large as the lower limit of theabove-mentioned range, various lithography properties (such as LWR) ofthe resist composition are improved. Further, a resist pattern having anexcellent shape can be obtained. On the other hand, when the amount ofthe component (D) is no more than the upper limit of the above-mentionedrange, sensitivity can be maintained at a satisfactory level, andthrough-put becomes excellent.

<Optional Components>

[Component (E)]

In the present embodiment, in the resist composition, for preventing anydeterioration in sensitivity, and improving the resist pattern shape andthe post exposure stability of the latent image formed by thepattern-wise exposure of the resist layer, at least one compound (E)(hereafter referred to as the component (E)) selected from the groupconsisting of an organic carboxylic acid, or a phosphorus oxo acid orderivative thereof can be added as an optional component.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid estersand phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

[Component (F)]

In the present embodiment, the resist composition of the presentembodiment may contain a fluorine additive (hereafter, referred to as“component (F)”) for imparting water repellency to the resist film.

As the component (F), for example, a fluorine-containing polymericcompound described in Japanese Unexamined Patent Application, FirstPublication No. 2010-002870, Japanese Unexamined Patent Application,First Publication No. 2010-032994, Japanese Unexamined PatentApplication, First Publication No. 2010-277043, Japanese UnexaminedPatent Application, First Publication No. 2011-13569, and JapaneseUnexamined Patent Application, First Publication No. 2011-128226 can beused.

Specific examples of the component (F) include polymers having astructural unit (f1) represented by general formula (f1-1) shown below.As the polymer, a polymer (homopolymer) consisting of a structural unit(f1) represented by formula (f1-1) shown below; a copolymer of astructural unit (f1) represented by formula (f1-1) shown below and theaforementioned structural unit (a1); and a copolymer of a structuralunit (f1) represented by formula (f1-1) shown below, a structural unitderived from acrylic acid or methacrylic acid and the aforementionedstructural unit (a1) are preferable. As the structural unit (a1) to becopolymerized with a structural unit (f1) represented by formula (f1-1)shown below, a structural unit derived from 1-ethyl-1-cyclooctyl(meth)acrylate or a structural unit represented by the aforementionedformula (a1-2-01) is preferable.

In the formula, R is the same as defined above; Rf¹⁰² and Rf¹⁰³ eachindependently represents a hydrogen atom, a halogen atom, an alkyl groupof 1 to 5 carbon atoms, or a halogenated alkyl group of 1 to 5 carbonatoms, provided that Rf¹⁰² and Rf¹⁰³ may be the same or different; nf¹represents an integer of 1 to 5; and Rf¹⁰¹ represents an organic groupcontaining a fluorine atom.

In formula (f1-1), R is the same as defined above. As R, a hydrogen atomor a methyl group is preferable.

In formula (f1-1), examples of the halogen atom for Rf¹⁰² and Rf¹⁰³include a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is particularly desirable. Examples of thealkyl group of 1 to 5 carbon atoms for Rf¹⁰² and Rf¹⁰³ include the samealkyl group of 1 to 5 carbon atoms as those described above for R, and amethyl group or an ethyl group is preferable. Specific examples of thehalogenated alkyl group of 1 to 5 carbon atoms represented by Rf¹⁰² orRf¹⁰³ include groups in which part or all of the hydrogen atoms of theaforementioned alkyl groups of 1 to 5 carbon atoms have been substitutedwith halogen atoms. Examples of the halogen atom include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is particularly desirable. Among these, as Rf¹⁰² and Rf¹⁰³, ahydrogen atom, a fluorine atom or an alkyl group of 1 to 5 carbon atomsis preferable, and a hydrogen atom, a fluorine atom, a methyl group oran ethyl group is more preferable.

In formula (f1-1), nf¹ represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2.

In formula (f1-1), Rf¹⁰¹ represents an organic group containing afluorine atom, and is preferably a hydrocarbon group containing afluorine atom.

The hydrocarbon group containing a fluorine atom may be linear, branchedor cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to15 carbon atoms, and most preferably 1 to 10 carbon atoms.

It is preferable that the hydrocarbon group having a fluorine atom has25% or more of the hydrogen atoms within the hydrocarbon groupfluorinated, more preferably 50% or more, and most preferably 60% ormore, as the hydrophobicity of the resist film during immersion exposureis enhanced.

Among these, as Rf¹⁰¹, a fluorinated hydrocarbon group of 1 to 5 carbonatoms is preferable, and a methyl group, —CH₂—CF₃, —CH₂—CF₂—CF₃,—CH(CF₃)₂, —CH₂—CH₂—CF₃, and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ are mostpreferable.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (F)is preferably 1,000 to 50,000, more preferably 5,000 to 40,000, and mostpreferably 10,000 to 30,000. When the weight average molecular weight isno more than the upper limit of the above-mentioned range, the resistcomposition exhibits a satisfactory solubility in a resist solvent. Onthe other hand, when the weight average molecular weight is at least aslarge as the lower limit of the above-mentioned range, dry etchingresistance and the cross-sectional shape of the resist pattern becomesatisfactory.

Further, the dispersity (Mw/Mn) of the component (F) is preferably 1.0to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

As the component (F), one type may be used alone, or two or more typesmay be used in combination.

The component (F) is generally used in an amount within a range from 0.5to 10 parts by weight, relative to 100 parts by weight of the component(A).

In the present embodiment, if desired, other miscible additives can alsobe added to the resist composition. Examples of such miscible additivesinclude additive resins for improving the performance of the resistfilm, dissolution inhibitors, plasticizers, stabilizers, colorants,halation prevention agents, and dyes.

[Component (S)]

In the present embodiment, the resist composition can be prepared bydissolving the materials for the resist composition in an organicsolvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone (MEK), cyclohexanone, methyl-n-pentylketone (2-heptanone) and methyl isopentyl ketone; polyhydric alcohols,such as ethylene glycol, diethylene glycol, propylene glycol anddipropylene glycol; compounds having an ester bond, such as ethyleneglycol monoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; aromatic organic solventssuch as anisole, ethylbenzylether, cresylmethylether, diphenylether,dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene; and dimethylsulfoxide (DMSO).

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, PGMEA, PGME, γ-butyrolactone and EL are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL or cyclohexanone is mixed as the polar solvent,the PGMEA:EL or cyclohexanone weight ratio is preferably from 1:9 to9:1, and more preferably from 2:8 to 8:2. Alternatively, when PGME ismixed as the polar solvent, the PGMEA:PGME weight ratio is preferablyfrom 1:9 to 9:1, more preferably from 2:8 to 8:2, and still morepreferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted in accordance with the thickness of the coatingfilm, at a concentration that enables favorable application of thecomposition to a substrate or the like. In general, the organic solventis used in an amount such that the solid content of the resistcomposition becomes within the range from 1 to 20% by weight, andpreferably from 2 to 15% by weight.

[Step B]

The present invention includes a step B of applying a cross-linkingcomposition so as to cover the first resist pattern formed in theaforementioned step A. The cross-linking composition applied in step Bis characterized by containing a blocked isocyanate compound having aprotected isocyanate group.

The blocked isocyanate compound is not particularly limited as long asthe protection of isocyanate group can be removed (also referred to asdeprotection or deblocking) in the heating step in step C describedlater.

Since the cross-linking composition containing the blocked isocyanatecompound which is deblocked by heating and regenerates an activeisocyanate group is used in the present invention, it is possible tothicken the first resist pattern without being affected by the design ofthe resist composition for forming the first resist pattern.

For example, in a method of thickening a pattern as described in PatentDocument 2, an acid generated from the first resist pattern is used forthe crosslinking reaction for thickening the pattern.

However, in this method, since the crosslinking reaction is affected bythe amount of acid on the first resist pattern, the range of options forthe resist composition for forming the first pattern becomes narrow.

On the other hand, a blocked isocyanate compound which is deblocked byheating and allows the crosslinking reaction to proceed is employed inthe present invention, thereby allowing the crosslinking reaction toproceed without being affected by the design of the resist compositionfor forming the first resist pattern.

[Blocked Isocyanate Compound]

In the blocked isocyanate compound of the present invention, deblockingoccurs, for example, as shown in the following reaction formula (BC)-1.The reaction formula (BC)-1 shown below is provided in order toillustrate an example of deblocking, and the present invention is by noway limited by the reaction formula.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ys⁰¹represents a divalent linking group; and B represents a protecting groupof an isocyanate group. In the formula, A represents a heating.

In the reaction formula (BC)-1, R is the same as defined above. Ys⁰¹represents a divalent linking group, and the divalent linking group forYs⁰¹ is the same as defined for the divalent linking group for Ya²¹ inthe aforementioned general formula (a2-1). Among the divalent linkinggroup for Ya²¹ in the aforementioned general formula (a2-1), a divalenthydrocarbon group which may have a substituent is preferable, and alinear or branched aliphatic hydrocarbon group of 1 to 10 carbon atomsis more preferable.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4,and most preferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

In reaction formula (BC)-1, B is a protecting group of the isocyanategroup, and more specifically represents a residual group of isocyanateprotection agent. Examples of the protection agent include phenol typecompound such as phenol, cresol, xylenol, ethylphenol,o-isopropylphenol, butylphenol (such as p-tert-butylphenol),p-tert-octylphenol, nonylphenol, dinonylphenol, styrenated phenol,oxybenzoic acid ester, thymol, p-naphthol, p-nitrophenol, p-chlorophenoland the like; alcohol type compound such as methanol, ethanol, propanol,butanol, ethylene glycol, methyl cellosolve, butyl cellosolve, methylcarbitol, benzyl alcohol, phenyl cellosolve, furfuryl alcohol,cyclohexanol and the like; active methylene type compound such asdimethyl malonate, diethyl malonate, methyl acetoacetate, ethylacetoacetate, acetylacetone and the like; mercaptan type compound suchas butyl mercaptan, thiophenol, tert-dodecyl mercaptan and the like;amine type compound such as diphenylamine, phenylnaphthylamine, aniline,carbazole and the like; acid amide type compound such as acetanilide,acetanisidide, acetic acid amide, benzamide and the like; lactam typecompound such as ε-caprolactam, δ-valerolactam, γ-butyrolactam,β-propiolactam and the like; acid imide type compound such as succinicacid imide, maleic acid imide and the like; imidazole type compound suchas imidazole, 2-methyl imidazole, 2-ethyl imidazole and the like;pyrazole type compound such as pyrazole, 3,5-dimethyl-1H-pyrazole andthe like; urea type compound such as urea, thiourea, ethylene urea andthe like; carbamide acid salt type compound such as N-phenyl carbamatephenyl, 2-oxazolidone and the like; imine type compound such as ethyleneimine, polyethylene imine, propane-2-imine and the like; oxime typecompound such as formaldoxime, acetaldoxime, acetone oxime, methyl ethylketoxime, methyl isobutyl ketoxime, cyclohexanone oxime and the like;bisulfite salt type compound such as sodium bisulfite, potassiumbisulfite and the like. As the protection agent, 1 kind of compound maybe used, or 2 or more kinds of compounds may be used in combination.

Among them, phenol type compound, lactam type compound, alcohol typecompound, oxim type compound, pyrazole type compound, and imine typecompound are preferable; nonylphenol, styrenated phenol, oxybenzoic acidester, acetoxime, methylethylketoxime, ε-caprolactam, pyrazole,3,5-dimethyl-1H-pyrazole and propan-2-imine are particularly preferable.

The term “residual group of an isocyanate protection agent” (protectinggroup) is a group in which a hydrogen atom has been removed from theaforementioned protection agent.

Although the protecting group protects an isocyanate group which hashigh reactivity, the isocyanate group is generated by heating above thedissociation temperature in order to eliminate the protecting group,thereby forming cross-linking structure with the first resist patternand thickening the pattern.

The reaction of an isocyanate compound with the protection agent can beconducted with or without the presence of a solvent. When using asolvent, it is necessary to use a solvent inert to isocyanate groups.During the blocking reaction, organic metal salts of tin, zinc, lead andthe like, tertiary amines, and the like may be used as a catalyst. Ingeneral, the reaction can be carried out at −20 to 150° C., although itis preferably carried out at 0 to 100° C.

In the present invention, when the first resist pattern covered with acrosslinking agent composition containing a protected blocked isocyanatecompound is heated to above the dissociation temperature, the protectinggroup is eliminated, and the generated isocyanate group reacts with aprimary or secondary hydroxyl group, or a primary or secondary aminogroup.

In the reaction formula (BC)-2 shown below, a mechanism of eliminationof the protecting group by heating and reaction of the generatedisocyanate group with the primary hydroxyl group is shown. The reactionformula (BC)-2 shown below is provided in order to illustrate amechanism of elimination of the protecting group by heating and reactionof the generated isocyanate group with the primary hydroxyl group, andthe present invention is by no way limited by the reaction formula.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ys⁰¹represents a divalent linking group; and B1 represents a residual groupof an isocyanate protection agent. In the formula, Δ represents aheating.

In the reaction formula (BC)-2, R and Ys⁰¹ are the same as definedabove. In reaction formula (BC)-2, B1 represents a residual group ofisocyanate protection agent. In the present embodiment, examples of B1include a group same as a residual group of isocyanate protection agentfor B.

In the present embodiment, when the first resist pattern covered with acrosslinking agent composition containing a protected blocked isocyanatecompound is heated to above the dissociation temperature, the firstresist pattern can be thickened and thus a reduced pattern can beformed.

The reason for this is that, in the case where a solvent-developednegative-tone pattern is formed as the first resist pattern to bethickened, a hydrophilic group will be present on the first resistpattern surface 2 a (see FIG. 1C).

Therefore, when the isocyanate group generated by the elimination of theprotecting group due to heating reacts with a primary or secondaryhydroxyl group, or a primary or secondary amino group, the crosslinkingreaction between the isocyanate group and a hydroxyl group, a lactone,an acid anhydride, an ester and the like (hereafter, referred to as a“hydroxyl group or the like”) on the first resist pattern surface isallowed to proceed, thereby forming a cross-linking structure. As aresult, the pattern is thickened.

In the present invention, the blocked isocyanate compound is preferablya compound represented by any one of general formulae (s0)-1 and (s0)-2shown below.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ys⁰¹represents a divalent linking group; Rs⁰¹ represents a residual group ofan isocyanate protection agent; and Rs⁰² and Rs⁰³ each independentlyrepresents a group selected from the group consisting of a methyl group,an ethyl group, an n-propyl group, an n-butyl group and an n-pentylgroup.

In general formula (s0)-1, R and Ys^(° 1) are the same as defined above.In general formula (s0)-1, Rs⁰¹ represents a residual group ofisocyanate protection agent.

Examples of the residual group of isocyanate protection agent for Rs⁰¹include the same residual groups of isocyanate protection agent as thosedescribed above for B. Further, as the residual group of an isocyanateprotection agent for Rs⁰¹, preferable examples includenitrogen-containing cyclic groups.

Examples of the nitrogen-containing cyclic group for Rs⁰¹ include groupsrepresented by formulae (bc-r-1) to (bc-r-8) shown below.

In the formula, Rs⁰⁰¹ represents an alkyl group of 1 to 5 carbon atoms;n represents an integer of 0 to 3; and * represents a valence bond.

Examples of the alkyl group of 1 to 5 carbon atoms for Rs⁰⁰¹ include amethyl group, an ethyl group, a propyl group, a butyl group and a pentylgroup, and a methyl group or an ethyl group is preferable.

Specific examples of compounds represented by general formula (s0)-1 areshown below.

In general formula (s0)-2, Rs⁰² and Rs⁰³ each independently represents agroup selected from the group consisting of a methyl group, an ethylgroup, an n-propyl group, an n-butyl group and an n-pentyl group; and amethyl group or an ethyl group is preferable. Specific examples ofcompounds represented by general formula (s0)-2 are shown below.

The blocked isocyanate compounds can also be obtained as commerciallyavailable products. As a commercially available product, Karenz MOI-BM(Trade Mark), Karenz MOI-BP (Trade Mark) (manufactured by Showa DenkoK.K.) and the like can be used.

The amount of the blocked isocyanate compound based on the total solidcontent of the cross-linking composition can be determined depending onthe kinds or the contents of solvents and the other resins. In general,the amount of the blocked isocyanate compound is preferably 1 to 100% byweight, more preferably 5 to 90% by weight, and still more preferably 10to 85% by weight.

[Polymeric Compound (BC)]

In the present embodiment, as the cross-linking composition, theaforementioned blocked isocyanate compound may be used alone, or apolymeric compound (BC) having a structural unit derived from theaforementioned blocked isocyanate compound and other structural unit maybe used. As the other structural unit, preferable examples include astructural unit (a1) containing an acid decomposable group whichexhibits increased polarity by the action of acid, a structural unit(a2) containing a lactone-containing cyclic group or a —SO₂— containingcyclic group, a structural unit (a4) containing an acid non-dissociablecyclic group, or a structural unit (st) derived from styrene describedbelow.

In the present invention, it is preferable to use the aforementionedblocked isocyanate compound alone, and a copolymer of a structural unitderived from the aforementioned blocked isocyanate compound and thestructural unit (a4) containing an acid non-dissociable cyclic group; acopolymer of a structural unit derived from the aforementioned blockedisocyanate compound and a structural unit (a1) containing an aciddecomposable group which exhibits increased polarity by the action ofacid; a copolymer of a structural unit derived from the aforementionedblocked isocyanate compound and the structural unit (a2) containing alactone-containing cyclic group; and a copolymer of a structural unitderived from the aforementioned blocked isocyanate compound and astructural unit (st) derived from styrene described below are morepreferable. Among them, the copolymer of a structural unit derived fromthe aforementioned blocked isocyanate compound and the structural unit(a4) containing an acid non-dissociable cyclic group is particularlydesirable.

In this case, the amount of each structural unit (a1) to (a2), (a4) and(st) based on the combined total of all structural units constitutingthe cross-linking composition is preferably 20 to 90 mol %, morepreferably 20 to 85 mol %, and still more preferably 30 to 80 mol %.

(Structural Unit (st))

In the present embodiment, the polymeric compound (BC) preferably has astructural unit derived from styrene (hereafter referred to as“structural unit (st)”).

Here, the term “styrene” refers to a general concept including styrene;compounds in which the hydrogen atom bonded to the carbon atom at theα-position of styrene has been substituted with another substituent suchas a halogen atom, an alkyl group or a halogenated alkyl group; andderivatives thereof (preferably, a compound having a substituent such asa substituent described in the explanation of a divalent linking groupfor Ya²¹ in the aforementioned general formula (a2-1), as a substituentbonded to the benzene ring). Here, the α-position (carbon atom on theα-position) of styrene refers to the carbon atom having the benzene ringbonded thereto, unless specified otherwise.

Specific examples of the structural unit (st) include a structural unit(st1) represented by general formula (st1-1) shown below.

In the formula, R^(st) represents a hydrogen atom or a methyl group; R⁰¹represents an alkyl group of 1 to 5 carbon atoms; and m₀₂ represents aninteger of 0 to 3.

In the structural unit (st1) represented by the aforementioned generalformula (st1-1), R^(st) represents a hydrogen atom or a methyl group,and a hydrogen atom is preferable.

R⁰¹ is preferably a linear or branched alkyl group of 1 to 5 carbonatoms, and specific examples thereof include a methyl group, an ethylgroup, a propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, a tert-butyl group, a pentyl group, an isopentyl group, and aneopentyl group. In terms of industry, a methyl group or an ethyl groupis preferable.

m₀₂ represents an integer of 0 to 3. Among these, m₀₂ is preferably 0 or1, and most preferably 0 from an industrial viewpoint.

When m₀₂ is 1, the substitution position of R⁰¹ may be any of theo-position, the m-position and the p-position. Further, when m₀₂ is 2 or3, a desired combination of the substitution positions can be used.

The polymeric compound (BC) can be obtained, for example, by aconventional radical polymerization or the like of the monomerscorresponding with each of the structural units, using a radicalpolymerization initiator such as azobisisobutyronitrile (AIBN) ordimethyl 2,2′-azobis(isobutyrate).

In the present embodiment, the weight average molecular weight (Mw) (thepolystyrene equivalent value determined by gel permeationchromatography) of the polymeric compound (BC) is not particularlylimited, but is preferably 1,000 to 10,000,000, more preferably 1,500 to500,000, and most preferably 2,000 to 300,000.

As the polymeric compound (BC), one type of compound may be used alone,or two or more types of compounds may be used in combination.

[Solvent]

A solvent contained in the cross-linking composition may be water or anorganic solvent and is not particularly limited as long as it does notdissolve the first resist pattern, and it can be appropriately selecteddepending on the kind of the cross-linking composition and the resistcomposition. When water is used as the solvent, pure water ispreferable. When an organic solvent is used as the solvent, ketonesolvents, ester solvents, alcohol solvents, amide solvents, ethersolvents and the like are preferable. These organic solvents may be usedalone, or two or more types may be used in combination.

Among these, in terms of not dissolving the first resist pattern, estersolvents are more preferable, and butyl acetate is particularlydesirable.

All the solid content within the cross-linking composition (total weightexcluding solvent) is preferably 0.1 to 20% by weight, more preferably0.1 to 10% by weight, and most preferably 0.1 to 5% by weight.

In the step of applying a cross-linking composition, the cross-linkingcomposition may be applied by any method as long as the composition canbe applied to the first resist pattern. A conventional spin-coatingmethod, a spray method, a roller-coating method, a dipping method andthe like can be used, and the spin-coating method is preferable.

[Step C]

The present invention includes a step C of heating the covered firstresist pattern and crosslinking an isocyanate group in the cross-linkingcomposition with the first resist pattern.

In the step C, the first resist pattern covered with the cross-linkingcomposition is heated after applying the cross-linking composition. Byvirtue of the step, the insoluble residual solvent can be removed.Furthermore, the blocked isocyanate compound is deprotected to generatean isocyanate group, thereby allowing the cross-linking reaction toproceed on the first resist pattern surface.

The heating temperature and the heating period can be appropriatelyselected depending on the types of the resist material, the types of thecross-linking composition, and the amount of shrinkage of the resistpattern. The heating temperature is preferably 80 to 200° C., and morepreferably 100 to 170° C. The heating period is preferably 30 to 300seconds, more preferably 30 to 120 seconds, and most preferably 30 to 80seconds.

[Step D]

The present invention includes a step D of developing the covered firstresist pattern.

In the step D, the excess cross-linking composition and the unreactedcross-linking composition in the aforementioned step C are removed.

The developing treatment is conducted using an alkali developingsolution in the case of an alkali developing process, and a developingsolution containing an organic solvent (organic developing solution) inthe case of a solvent developing process.

After the developing treatment, it is preferable to conduct a rinsetreatment. In the case of an alkali developing process, the rinsetreatment is preferably performed using pure water, whereas in the caseof a solvent developing process, the rinse treatment is preferablyperformed using a rinse liquid containing an organic solvent.

In the case of a solvent developing process, residual developingsolution or rinse liquid adhered to the pattern following the developingtreatment or rinse treatment may be removed using a supercritical fluid.

Drying is performed following the developing treatment or rinsetreatment. If desired, bake treatment (post bake) can be conductedfollowing the developing. In this manner, a resist pattern can beobtained.

In the present embodiment, the developing treatment may be an alkalideveloping process or may be a solvent developing process, however, interms of removal efficiency of the cross-linking composition, thesolvent developing process is preferable. In the step D, as shown inFIG. 1D, a cross-linked structure forming portion 2 a is formed on thesurface of the first resist pattern 2, thereby forming a thickenedpattern. As a result, in the case of a hole pattern, a reduced patternin which the hole diameter is reduced is formed, whereas a reducedpattern in which the space width is reduced is formed in a line andspace pattern.

Examples

The present invention will be described more specifically with referenceto the following examples, although the scope of the present inventionis by no way limited by these examples.

[Step A]

<Preparation of Resist Composition>

100 parts by weight of a polymeric compound (A)-1 shown below; 6 partsby weight of a compound (B)-1 shown below; 3 parts by weight of acompound (D)-1 shown below; 1.5 parts by weight of a polymeric compound(F)-1 shown below; 100 parts by weight of γ-butyrolactone; and 4,000parts by weight of a solvent (mixed solvent ofPGMEA/PGME/cyclohexanone=45/30/25 (weight ratio)) were mixed together toprepare a resist composition.

<Formation of Resist Pattern>

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied onto an 12-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicanti-reflection film having a film thickness of 85 nm.

Then, the resist composition obtained above was applied to the filmusing a spinner, and was then prebaked (PAB) on a hotplate at 105° C.for 60 seconds and dried, thereby forming a resist film having a filmthickness of 85 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask pattern (6% halftone), using anexposure apparatus NSR-S609B (manufactured by Nikon Corporation,NA=1.07, Annular).

Then, development was conducted using butyl acetate for 13 seconds.

Then, a post exposure bake (PEB) treatment was conducted at 80° C. for60 seconds.

As a result, hole pattern (hereafter, sometimes referred to as “firstresist pattern”) described below was formed.

Target 1: 75 nm mask/110 nm pitch/60 nm CH

Target 2: 155 nm mask/300 nm pitch/60 nm CH

[Step B]

<Preparation of Cross-Linking Composition>

[Synthesis of Polymeric Compound]

In a separable flask equipped with a thermometer, a reflux tube and anitrogen feeding pipe, 25.00 g (113.48 mmol) of the compound 1, 7.58 g(30.16 mmol) of the compound 2 were dissolved in 48.87 g of methyl ethylketone (MEK). Then, 11.49 mmol of dimethyl 2,2′-azobis(isobutyrate)(V-601) as a polymerization initiator was added and dissolved in theobtained solution to prepare a dripping solution.

The dripping solution was dropwise added to 17.28 g of MEK heated to 80°C. in a nitrogen atmosphere over 4 hours. Thereafter, the reactionsolution was heated for 1 hour while stirring, and then cooled to roomtemperature.

The obtained reaction polymerization solution was dropwise added to anexcess amount of n-heptane to deposit a polymer. Thereafter, theprecipitated white powder was separated by filtration, followed bywashing with n-heptane, and then drying, thereby obtaining 23.46 g of apolymeric compound 3 as an objective compound.

With respect to the polymeric compound, the weight average molecularweight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,700, and the dispersity was 1.90.

Further, the compositional ratio of the copolymer (the proportion (molarratio) of each of the structural units within the structural formula)determined by carbon-13 nuclear magnetic resonance spectroscopy (600MHz, ¹³C-NMR) was 1/m=79.9/20.1.

Other polymeric compounds 1 and 2 and 4 to 11 were also synthesized inthe same manner as the polymeric compound 3.

Then, the polymeric compounds 1 to 11 shown in Table 1 were eachdissolved in butyl acetate, thereby preparing cross-linking compositions1 to 11 (1.6% butyl acetate solutions of the polymeric compounds).

TABLE 1 Polymeric compound Composition Mw Mw/Mn 1 (BC-01) 9,500 2.10[100] 2 (a1-01)/(BC-01) 6,500 1.28 [35.7/64.3] 3 (a4-01)/(BC-01) 7,7001.90 [79.9/20.1] 4 (a4-01)/(BC-01) 8,200 1.84 [49.0/51.0] 5(a4-01)/(BC-01) 22,700 2.07 [49.1/50.9] 6 (a4-01)/(BC-01) 53,800 2.39[49.6/50.4] 7 (a4-01)/(BC-01) 82,300 2.37 [50.9/49.1] 8(a4-01)/(a4-02)/(BC-01) 83,400 2.43 [30.3/20.1/49.6] 9(a4-01)/(a4-02)/(BC-01) 81,200 2.55 [10.1/39.7/50.2] 10 (a2-01)/(BC-01)8,900 1.89 [49.3/50.7] 11 (st-01)/(BC-01) 9,200 1.87 [49.4/50.6]

In Table 1, the reference characters in the composition sectionrepresent the following monomers. Further, the values in brackets [ ]indicate the amount (in terms of parts by weight) of the componentadded.

<Application of Cross-Linking Composition>

The cross-linking compositions 1 to 11 were applied using a spinner soas to cover the obtained first resist pattern. The cross-linkingcompositions 1 to 11 were regarded as Examples 1 to 11, respectively.

The coating film thickness of the cross-linking composition was 60 nm.

[Step C]

The isocyanate group in the cross-linking composition was cross-linkedwith the first resist pattern by heating the first resist pattern thatis covered with the cross-linking composition and obtained in [Step B]described above. The heating temperature is indicated under “Shrink bake(° C.)” in Tables 2 and 3 below. The heating time was 60 seconds.

[Step D]

After [Step C], development was conducted using butyl acetate for 13seconds, thereby removing the uncrosslinked portions of thecross-linking composition. As a result, the first resist pattern wasthickened, thereby forming a shrunk pattern in which the hole diameterwas reduced.

TABLE 2 Shrink S.V. (nm) I-D Bake Dose S.V. (nm) 155M/ Bias (° C.)(mJ/cm²) 75M/110P 300P (nm) Scum Example 1 100 33 1.6 1.2 −0.4 A 130 339.3 6.6 −2.7 A 160 33 — — — — Example 2 100 33 3.7 1.9 −1.8 A 130 33 4.50.4 −4.1 A 160 33 — — — — Example 3 100 33 4.2 1.9 −2.3 A 130 33 6.0 5.5−0.5 A 160 33 7.1 5.8 −1.3 A Example 4 100 33 3.4 1.8 −1.6 A 130 33 4.31.7 −2.6 A 160 33 9.3 7.5 −1.8 A

TABLE 3 Shrink I-D Bake Dose S.V. (nm) S.V. (nm) Bias (° C.) (mJ/cm²)75M/110P 155M/300P (nm) Scum Example 5 160 33 17.2 17.2 0.0 A Example 6160 33 28.8 29.5 0.7 B Example 7 160 33 32.3 31.6 −0.7 B Example 8 12033 15.9 17.7 1.8 A 130 33 22.8 21.3 −1.5 B 140 33 26.8 27.6 0.9 BExample 9 130 33 20.8 17.4 −3.4 B Example 160 33 14.5 15.6 1.1 A 10Example 160 33 16.2 16.4 0.2 A 11

In Tables 2 and 3, “S.V. (nm) 75M/110P” indicates the difference fromthe hole diameter of the first resist pattern in a 110 nm pitch pattern,and “S.V. (nm) 155M/300P” indicates the difference from the holediameter of the first resist pattern in a 300 nm pitch pattern. Further,“I-D Bias (nm)” indicates the difference between “S.V. (nm) 75M/110P”and “S.V. (nm) 155M/300P”.

[Scum Evaluation]

The shape of the pattern obtained above was observed using a criticaldimension scanning electron microscope (SEM) and a cross section SEM,and the generation of scum was evaluated by the following criteria.

(Criteria)

A: scum was not generated after the development.

B: scum was slightly generated after the development.

As seen from the results shown above, in Examples 1 to 11 in which thecross-linked structures were formed by applying the cross-linkingcompositions, followed by heating, the difference with the hole diameterof the first resist pattern was large and the patterns were successfullyshrunk in a favorable manner.

DESCRIPTION OF REFERENCE SYMBOLS

-   -   1: substrate, 2: first resist pattern, 3: cross-linking        composition layer, 2 a: cross-linked structure forming portion

What is claimed is:
 1. A method of forming a resist pattern, comprising:forming a first resist pattern on a substrate; applying a cross-linkingcomposition so as to cover the first resist pattern; heating the coveredfirst resist pattern and crosslinking an isocyanate group in thecross-linking composition with the first resist pattern; and developingthe covered first resist pattern, wherein the cross-linking compositioncomprises a blocked isocyanate compound having a protected isocyanategroup.
 2. The method of forming a resist pattern according to claim 1,wherein the blocked isocyanate compound is a compound represented bygeneral formula (s0) shown below:

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ys⁰¹represents a single bond or a divalent linking group; and Rs⁰¹represents a residual group of isocyanate protection agent.
 3. Themethod of forming a resist pattern according to claim 2, wherein Rs^(O1)represents a nitrogen-containing cyclic group.
 4. The method of forminga resist pattern according to claim 3, wherein the nitrogen-containingcyclic group is a group represented by any one of formulae (bc-r-1) to(bc-r-8) shown below:

wherein Rs⁰⁰¹ represents an alkyl group of 1 to 5 carbon atoms; nrepresents an integer of 0 to 3; and * represents a valence bond.
 5. Themethod of forming a resist pattern according to claim 1, wherein theblocked isocyanate compound is a compound represented by general formula(s0)-1 or (s0)-2 shown below:

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; Ys⁰¹represents a divalent linking group; Rs⁰¹ represents a residual group ofan isocyanate protection agent; and Rs⁰² and Rs⁰³ each independentlyrepresents a group selected from the group consisting of a methyl group,an ethyl group, an n-propyl group, an n-butyl group and an n-pentylgroup.
 6. The method of forming a resist pattern according to claim 5,wherein Rs⁰¹ represents a nitrogen-containing cyclic group.
 7. Themethod of forming a resist pattern according to claim 6, wherein thenitrogen-containing cyclic group is a group represented by any one offormulae (bc-r-1) to (bc-r-8) shown below:

wherein Rs⁰⁰¹ represents an alkyl group of 1 to 5 carbon atoms; nrepresents an integer of 0 to 3; and * represents a valence bond.
 8. Themethod of forming a resist pattern according to claim 1, wherein thecross-linking composition comprises a copolymer of a structural unitderived from the blocked isocyanate compound and one or more structuralunits selected from the group consisting of a structural unit containingan acid decomposable group which exhibits increased polarity by actionof acid, a structural unit containing a lactone-containing cyclic groupor a —SO₂— containing cyclic group, and a structural unit containing anacid non-dissociable cyclic group.
 9. The method of forming a resistpattern according to claim 1, wherein the first resist pattern is asolvent-developed negative-tone resist pattern.
 10. The method offorming a resist pattern according to claim 2, wherein the first resistpattern is a solvent-developed negative-tone resist pattern.
 11. Themethod of forming a resist pattern according to claim 3, wherein thefirst resist pattern is a solvent-developed negative-tone resistpattern.
 12. The method of forming a resist pattern according to claim4, wherein the first resist pattern is a solvent-developed negative-toneresist pattern.
 13. The method of forming a resist pattern according toclaim 5, wherein the first resist pattern is a solvent-developednegative-tone resist pattern.
 14. The method of forming a resist patternaccording to claim 6, wherein the first resist pattern is asolvent-developed negative-tone resist pattern.
 15. The method offorming a resist pattern according to claim 7, wherein the first resistpattern is a solvent-developed negative-tone resist pattern.
 16. Themethod of forming a resist pattern according to claim 8, wherein thefirst resist pattern is a solvent-developed negative-tone resistpattern.